Sir Josse d’Acquin: French knight, and Abbess Helewise, at the Hawkenly Abbey in England during the 12th century, by Alys Clare

Serendipity Dahlquist: gum-snapping 15-year-old girl, and Leo Bloodworth, a grumpy 50-something private investigator, in Los Angeles, California, by Dick Lochte

Mike Daley: lawyer and ex-priest, in San Francisco, California, by Sheldon Siegel

Adam Dalgliesh: critically acclaimed poet and Scotland Yard commander, in London, England, by P.D. James

Isabel Dalhousie: Scottish-American editor of the esteemed Review of Applied Ethics and a woman of independent means in Edinburgh, Scotland, in the Sunday Philosophy Club mysteries by Alexander McCall Smith

Eve Dallas: homicide lieutenant in futuristic New York City, by J.D. Robb

Nick Dallas: young but retired cop, now a private investigator, in 1950s Detroit, Michigan, by P.S. Elsner

Daisy Dalrymple: a journalist in Hampshire, England, by Carola Dunn

Quintilian Dalrymple: private investigator in 2020s Edinburgh, Scotland, by Paul Johnston

Joe Dalton: sheriff in Metropolis, Illinois, by Lonnie Cruse

Micah Dalton: “cleaner” for the CIA, roaming the world to fix up Company messes, by David Stone

Smokey Dalton: African-American unlicensed private investigator, in Memphis, Tennessee, by Kris Nelscott

Justine Dalvik: in Hässelby, Sweden, by Inger Frimansson

Superintendent Andrew Dalziel and Sergeant Peter Pascoe, a pair of police inspectors in Yorkshire, England, by Reginald Hill

Gloria Damasco: Hispanic detective in the San Francisco Bay Area, in California, in the Brown Angel mysteries, by Lucha Corpi

Bill Damen: filmmaker turned sleuth, in the San Francisco Bay Area, California, by James Calder

Kathryn Dance: investigator with the California Bureau of Investigation, by Jeffery Deaver

April Dancer: the Girl from U.N.C.L.E. (TV tie-in), by Michael Avalone

Eddie Dancer: ex-cop private investigator in Calgary, Alberta, Canada, by Mike Harrison

Jim Dandy: retired physical therapist, and Dodee Swisher, a gallery owner, in North America, in the Elderhostel Mysteries by Peter Abresch

Timothy Dane: private investigator in New York City, by William Ard

Abigail Patience Danforth: 19th century heiress detective, by Marian J. A. Jackson

Daniel Kearney Associates: auto repo and skip-tracing firm, in San Francisco, California, by Joe Gores

Judah Daniel: freedwoman who is also the local herbalist, and Narcissa Power, a young widow, at the time of the Civil War in Virginia, by Ann McMillan

Louisa Danie: 60-ish social worker, and later her daughter Emily and son-in-law David, by Malinda M. Hall

Charmian Daniels: police detective in Deerham Hills, England, by Jennie Melville (Gwendoline Butler)

Lt. Jacqueline “Jack” Daniels: in the Violent Crimes unit in Chicago, Illinois, by J.A. Konrath

Peaches Dann: absent-minded 50-something widow in North Carolina, by Elizabeth Daniels Squire

Dick Dansoir: gay personal trainer and occasional go-go dancer at the boys' bars in New Orleans, Louisiana, by Greg Herren

Joe Dante: maverick cop in New York City, by Christopher Newman

Michel Danton: police detective in the south of France, by Norman Bogner

Fitzwilliam Darcy and Elizabeth Bennet, taking up the story ended in Jane Austen’s Pride and Prejudice, in Regency (early 1800s) England, by Carrie Bebris

Meg Darcy: working-class lesbian private investigator, and police detective Sarah Lindstrom, in St. Louis, Missouri, by Jean Marcy

Tess Darcy: bed-and-breakfast owner in Victoria Springs, Missouri, in the Iris House mysteries, by Jean Hager

Madeline Dare: former dubutante in 1980s New York and Massachusetts, by Cornelia Read

Max Darling: investigator, and Annie Laurance, a mystery book store owner, in Broward’s Rock, South Carolina, in the Death on Demand series, by Carolyn G. Hart

Professor John Darnell: detective debunking supernatural theories early in the 20th century, by Sam McCarver

Sigismondo da Roca: Italian agent of a Renaissance duke by Elizabeth Eyre (Susannah Stacey)

D’Artagnan, Athos, Porthos, and Aramis, of Dumas fame, serving the king in 17th century France, in the Musketeers mysteries, by Sarah D’Almeida

Jan Da Silva: lounge singer and private detective, in Seattle, Washington, by K.K. Beck

Captain Jose da Silva: supercop in Rio de Janeiro, Brazil, by Robert L. Fish

Dave: ex-cop investigator, and Mom, Dave’s mother, in Mesa Grande, Colorado, by James Yaffee

Alphonse "Dave" Davecki: police detective in Superior, Wisconsin, by Mike Savage

“Dangerous” Davies: detective constable in north London, England, by Leslie Thomas

Lucas Davenport: police detective and war games designer in Minneapolis, Minnesota, by John Sandford

John Davies: by Margot Bennett 

Dr. R.V. Davie: of St. Nicholas College, Cambridge, England, by V.C. Clinton-Baddeley

Rebecca Davies: child of privilege running a home for desperate women, and Marshall Webb, Rebecca’s beau, a freelance reporter for Harper’s Weekly who secretly pens dime novels, by Troy Soos

Queenie Davilov: struggling screenwriter and investigator in Hollywood, California, by Denise Osborne

Georgia Davis: ex-cop private investigator, in Chicago, Illinois, by Libby Fischer Hellmann

Angie DaVito: TV soap opera producer in New York City, by Louise Shaffer

Patrick Dawlish: who works with British Intelligence and later at Scotland Yard, by Gordon Ashe (John Creasey)

Carla Day: 20-something, and her elderly father, an accomplished Egyptologist suffering from Alzeimer’s, in California, by Diana O’Hehir

Jane Day: newspaper reporter, and Jerry Knight, a talk show host, in Washington DC, by Ron Nessen and Johanna Neuman

Julian Day: seeking revenge against those who ruined his career:, by Dennis Wheatley

Mechelle Deakes: African-American police detective demoted to the cold case unit, in Atlanta, Georgia, by Lynn Abercrombie (Walter Sorrells)

John Deal: building contractor in Miami, Florida, by Les Standiford

Sam Dean: Jamaica-born black journalist in London, England, by Mike Phillips

Sarah Deane: graduate student, and Alex McKenzie, a doctor in Maine, by J.S. Borthwick

Eve DeCateur, ex-beauty queen, and Annie Capshaw, recently divorced, in Arlington, Virginia, in the Cooking Class mysteries by Miranda Bliss

Commander Bill Decker, Mitch Taylor, Jub Freeman, police detectives in New York City, by Lawrence Treat

Peter Decker: LAPD detective, and his wife Rina Lazarus, in Los Angeles, California, by Faye Kellerman

Robert De Clerq: member of the Special X department of the Royal Canadian Mounted Police in Vancouver, British Columbia, Canada, by Michael Slade

Mr. Dee: in England by Desmond Cory

Judge Dee: magistrate in China during the Tang Dynasty (600s), by Robert Van Gulik

Catherine “Cat” Deean: part-owner of a catering enterprise in Los Angeles, California, in the the Mysteries for Food Lovers, by Cynthia Lawrence

Carolus Deene: ex-commando turned schoolmaster in England, by Leo Bruce

Howard Moon Deer: private investigator in San Geronimo, New Mexico, by Robert Westbrook

Rinus de Gier, Henk Grijpstra, and the Commisaris, police detectives in Amsterdam, The Netherlands by Janwillem Van de Wetering

Dr. Gerritt DeGraaf: forensic pathologist in Chicago, Illinois, by Barbara D’Amato

Jurrian DeKok: (De Cock in original publications), detective inspector in the police department, in Amsterdam, The Netherlands, by A.C. Baantjer

Kate Delafield: lesbian homicide detective in Los Angeles, California, by Katherine V. Forrest

Edward X. “Iron Balls” Delaney: retired chief of detectives in New YorkCity, by Lawrence Sanders

Evan Delaney: adventurous young woman in Santa Barbara, California, by Meg Gardiner

McLeod Delaney: Pulitzer-Prize-winning journalist from Florida, who comes to Princeton University as a visiting lecturer, later professor, in Princeton, New Jersey, by Ann Waldron

Patricia Delaney: private investigator in Cincinnati, Ohio, by Sharon Gwyn Short

Sarah Booth Delaney: unconventional Southern Belle in Zinnia, Mississippi, in the Southern Belle mysteries by Carolyn Haines

Alex Delaware: child psychologist in Los Angeles, California, by Jonathan Kellerman

Jade del Cameron: ambulance driver in WWI and adventurer in 1919-1920s colonial East Africa, by Suzanne Arruda

Kit DeLeeuw: Wall Street shark turned suburban detective in Rochambeau, New Jersey, by Jon Katz

Ralph Delchard: soldier and Gervase Bret, a lawyer, in 11th century England, in the Domesday Series, by Edward Marston

Alex Delillo: police detective lieutenant in Pasadena, California, by Scott Frost

Jack Delmas: private investigator from the Mississippi Gulf Coast, by Martin Hegwood

Commissario De Luca: former commander in Mussolini’s political police, in northern Italy in 1945, by Carlo Lucarelli

Nick Delvecchio: private investigator in Brooklyn, New York, by Robert J. Randisi

Gregor Demarkian: former FBI department head in Philadelphia, Pennsylvania, by Jane Haddam

Johnny DeMarco: fter five years as a private investigator, wins a comeback fight at age 40 in Brooklyn, New York, by Frank Megna

Mary Teresa Dempsey: 5'2" 200 lb. nun in Chicago, Illinois, by Monica Quill (Ralph M. McInerny)

Skye Denison: school psychologist in Scumble River, Illinois, by Denise Swanson

Sergeant Denny and Major Mearns special agents for William Pitt to watch George III, in England, by Gwendoline Butler

John Denson ex-reporter and ex-army intelligence operative, in Seattle, Washington, by Richard Hoyt

Harry James Denton: ex-newspaper reporter turned private investigator in Nashville, Tennessee, by Steve Womack

Department Z: and tales of British counterespionage, by John Creasey

Justin de Quincy: bastard son of a bishop in 12th century England, by Sharon Kay Penman

Duke de Richleau, an exiled French monarchist, along with “Modern Musketeers” Richard Eaton, a conservative Christian Englishman, Simon Aron, a liberal Jew, and American Rex Van Ryn, from 1894-1960, by Dennis Wheatley

Devereaux: AKA The November Man, a field intelligence agent for R Section, in New York City, by Bill Granger

Fever Devilin: folklorist and native of the Georgia Appalachians, by Phillip DePoy

Jude Devine: lesbian ex-FBI agent, now a Montezuma County Sheriff’s detective in Utah, by Rose Beecham

Harry Devlin: solicitor in Liverpool, England, by Martin Edwards

Jack Devlin: ex-Secret Service agent turned security firm investigator, in the USA, by John Clarkson

Liam Devlin: 1940s IRA hero in Ireland, by Jack Higgins

Matt Devlin: private eye, and Brooke Cassidy, a mystery writer, in 1890s Newport, Rhode Island, by Mary Kruger

Paul Devlin: police detective in New York City, by William Heffernan

Betsy Devonshire: needlework shop owner in Excelsior, Minnesota, by Monica Ferris

Timothy Dewer: police inspector in England, by Hilary Landon (George Bellairs)

Holly Dewitt: film producer and single mother in Miami, Florida, by Sherryl Woods

Sir John de Wolfe: the crowner (coroner), in 12th century Devon, England, in the Crowner John series by Bernard Knight

Emma Diamond: recent widow, novice bridge player, and amateur detective, in Houston, Texas, in the Bridge Club mysteries by Honor Hartman (Dean James)

Eve Diamond: reporter for the Los Angeles Times, in Los Angeles, California, by Denise Hamilton

Jake Diamond: private investigator who is more over-easy than hard-boiled, in San Francisco, California, by J.L. Abramo

Peter Diamond: ex-cop in Bath, England, by Peter Lovesey

Venus Diamond: U.S. Fish & Wildlife agent in Washington, by Skye Kathleen Moody

Don Diavolo by Stuart Towne (Clayton Rawson)

Charles Dickens and Wilkie Collins, 19th century writers in London, England, by  William J. Palmer

Auguste Didier: master chef in Victorian London, England, by Amy Myers

Alessandro Di Ganzarello, Jennifer Norrington, and Coleridge Tucker, a James Bond-like trio in London, England, by Ivor Drummond (Roger Erskine Longrigg)

George Porter Dillman: yacht-builder-turned-actor-turned-detective, by Conrad Allen (Edward Marston)

Sean Dillon: RA enforcer turned British special agent, in Ireland, by Jack Higgins

Jeff DiMarco: insurance investigator in Boston, Massachusetts, by Doris Miles Disney

Aunt Dimity: a romantic ghost in England, by Nancy Atherton

Laura Di Palma: corporate lawyer in San Francisco, California, by Lia Matera

Maisie Dobbs: psychologist and investigator based in 1920s and 1930s London, England, by Jacqueline Winspear

John Dobie: Professor of Mathematics in Cardiff, Wales, by Desmond Cory

Bobby Dodge: a state police sniper, and D.D. Warren, a police detective, in Boston, Massachusetts, by Lisa Gardner

Lark Dodge: bookseller in Shoalwater, Washington, by Sheila Simonson

Trixie Dolan and Evangeline Sinclair, aging actresses in London, England, by Marian Babson

Ulysses Finnegan Donaghue: Shakespeare scholar and private eye in Provence, France, by Anna Shone

Neal Donahoe: Harbor Patrol officer, and Tory Lennox, a Coast Guard lieutenant, in Santa Barbara, California, by Tony Gibbs

Donovan: assistant to Danny Coyle, a gambler, by Judson Philips

Donovan family, involved in a global gem-trading empire, based in Seattle, Washington, by Elizabeth Lowell (A.E. Maxwell)

Bill Donovan: Chief of Special Investigation, in New York City, by Michael Jahn

Cal Donovan, Frank Shapiro, and Liz Graham, cops in Castlemere, England, by Jo Bannister

Jake Donovan: FBI profiler by John E. Douglas

Joe Donovan: former investigative journalist whose son has disappeared, in Newcastle, England, by Martyn Waites

Paul Donavan: by Carter Brown

Delilah Doolittle: British widow and pet detective, and Watson, her Doberman pinscher, in fictional Surf City (Huntington Beach), California, by Patricia Guiver

Carroll Dorsey: private investigator in Pittsburgh, Pennsylvania, by Thomas Lipinski

John Dortmunder: criminal master planner in New York City, by Donald E. Westlake

William Dougal: post-grad student and security firm employee, in England, by Andrew Taylor

Wilfred Dover: fat lout of a Chief Inspector in England, by Joyce Porter

Father Roger Dowling: St. Hilary’s parish priest in Fox River, Illinois, by Ralph M. McInerny

Arthur Doyle: young doctor, and Joseph Bell, a doctor and Doyle’s mentor, in Edinburgh, Scotland, by David Pirie

Jack Doyle: failed ad-man and reluctant sleuth working in the horse-racing world, based in the Chicago, Illinois area, by John McEvoy

Molly Doyle: antiques dealer in Carmel, California, by Elaine Flinn

Jessie Drake: homicide detective in Los Angeles, California, by Rochelle Krich

Stephen Drake: newspaper reporter with ESP in San Francisco, California, by Collin Wilcox

Stud Draqual: maybe gay, maybe not CEO of Draqual Fashions, and a much-in-demand New York City haute-couture fashion designer of ladies' silk underwear, by William Maltese

Harry Dresden: the only wizard listed in the yellow pages in Chicago, Illinois, in the Dresden Files by Jim Butcher

Sir Clinton Driffield: Chief Constable, and Squire Wendover, in rural England, by J.J. Connington

Clifford Driscoll: no-named American spy in New York City, by William L. DeAndrea

John W. Driscoll: homicide detective lieutenant in New York City, by Thomas O’Callaghan

Jimmy Drover: ex-sportswriter in Chicago, Illinois, by Bill Granger

Chester Drum: ex-FBI agent private investigator, venturing around the world, by Stephen Marlowe

Major Sean “Bulldog” Drummond: lawyer in the army's Judge Advocate General Corps (JAG), by Brian Haig

Alex Duarte: ATF agent and Bosnia veteran, by James O. Born

Tubby Dubonnet: lawyer in New Orleans, Louisiana, by Tony Dunbar

MacDougal Duff: retired history professor in New York City, by Charlotte Armstrong

Nick Duffy: bisexual ex-cop turned private investigator, in London, England, by Dan Kavanagh

Dugan: a lawyer, and his wife Kirsten, owner of the Wild Onion, Ltd, a private detective agency, in Chicago, Illinois, by David J. Walker

Max Dumas: by Carter Brown

Eve Duncan: forensic sculptor by Iris Johansen

Vanessa Duncan: schoolteacher in late 19th century Cambridge, England, by Catherine Shaw

Tom Dunjer: in the future, by Isidore Haiblum

Luke Dunlop: an agent for the Witness Protection Agency in Australia, by Peter Corris

Mara Dunn: French-Canadian interior decorator, relocated to the Dordogne region in southwestern France, by Michelle Wan

Micah Dunn: a private investigator in New Orleans, Louisiana by M.K. (Malcolm) Shuman

Okie Dunn: appointed sheriff in 1930s Vernon, Oklahoma, by Fred Harris

Fintan Dunne: hard-boiled detective in pre-World War II New York City, by Peter Quinn

C. Auguste Dupin: detective in the first “real” detective story, by Edgar Allan Poe

Gabriel Du Pré: Métis (Cree and French, maybe a little English) cattle inspector and sometimes sheriff in Montana, by Peter Bowen

M. Dupuy by Anthony Gilbert

Quincy Durant and Artie Wu, a couple of soldiers of fortune for their company, WuDu Ltd., by Ross Thomas

Sam Durell: Cajun CIA operative, by Edwards S. Aarons and later Will. B. Aarons

Starletta Duvall: black homicide lieutenant in Brookport, Massachusetts, by Judith Smith-Levin

Jack Dwyer: ex-cop, part-time actor, and security guard, in Cedar Rapids, Iowa, by Ed Gorman

Billy Dye: struggling author, and Rawhead, an assassin and Dye’s childhood friend, in Manchester, England, by David Bowker

Mandy Dyer: owner of Dyer's Cleaners in Denver, Colorado, by Dolores Johnson

Toby Dyke: reporter in Devon, England, by E.X. Ferrars

Lindsey Dyson: investigative reporter by Calley Moore