Sano Ichiro: samurai and private investigator for the shogun, in the 1600s in Edo, Japan, by Laura Joh Rowland

Inspector Çetin Ikmen: policeman in Istanbul, Turkey, by Barbara Nadel

Desmond Iles: assistant chief constable, and Colin Harpur, detective chief superintendent, in an English seaport, by Bill James

Iliona: high priestess blackmailed into spying for Sparta, in 5th century BCE Greece, by Marilyn Todd

John Ingram: in South Pacific thrillers by Charles Williams

Nelson Ingram: burnt-out reporter, digging up the dark criminal secrets beneath the sleepy surface of Litchfield, Alabama, by Stephen J. Clark

Callum “Cal” Innes: an ex-con working as an unlicensed private investigator, in Manchester, England, by Ray Banks

Jack Irish: lawyer and gambler, turned debt collector and people finder, in Melbourne, Australia, by Peter Temple

Isaac: blind physician, and Bishop Berenguer, in 1350s Girona, Spain, by Caroline Roe

Hannah Ives: breast-cancer survivor and down-sizing victim, in Annapolis, Maryland, by Marcia Talley

Kate Ivory: novelist turned amateur detective in Oxford, England by Veronica Stallwood