Which character is known by the nickname Littlefinger?

The character known by the nickname Littlefinger is Petyr Baelish.

Petyr Baelish is a political operator in Game of Thrones and George R. R. Martin's A Song of Ice and Fire novels. He rises from a minor noble family to become Master of Coin on King Robert Baratheon's small council, using loans, alliances, secrets, and carefully timed betrayals to expand his influence.

The nickname has two related origins. Baelish's family comes from the Fingers, a group of small peninsulas, and Petyr was shorter than many of the lords among whom he grew up. Edmure Tully reportedly gave him the name during Petyr's childhood at Riverrun.

Littlefinger is often confused with Varys, another master of intrigue at the royal court. Their methods differ: Varys presents himself as a keeper of information serving the realm, while Baelish openly treats chaos and self-interest as routes to power. His schemes help trigger several major political crises.