4 (New York City Subway service)

	Lexington Avenue Express
	A Woodlawn-bound 4 train of R142As leaving Bedford Park Boulevard–Lehman College.
	Note: dashed line shows late night and limited weekday rush hour service to/from New Lots Avenue
Northern end	Woodlawn
Southern end	Crown Heights–Utica Avenue (daytime) ; New Lots Avenue (late nights & limited rush hour service)
Stations	28; 54 (late night service)
Rolling stock	R142; R142A; (Rolling stock assignments subject to change)
Depot	Jerome Yard
Started service	June 2, 1917
Route map
	The Bronx
	Manhattan
	switches to local tracks
	during late nights
	northbound local
	only
	southbound
	only
	switches to local tracks
	during late nights
	Manhattan
	Brooklyn
	northbound only
	for 4 and 5 services
	southbound
	only
	switches to local tracks
	during late nights

The 4 Lexington Avenue Express is a rapid transit service in the A Division of the New York City Subway. Its route emblem, or "bullet", is colored forest green since it uses the IRT Lexington Avenue Line in Manhattan.

The 4 operates 24 hours daily, although service patterns vary based on the time of day. Daytime service operates between Woodlawn in the Bronx and Utica Avenue in Crown Heights, Brooklyn, making all stops in Bronx and express stops in Manhattan and in Brooklyn; limited rush hour service, as well as overnight service, is extended beyond Utica Avenue and originates and terminates at New Lots Avenue in East New York, Brooklyn. During rush hours in the peak direction, the 4 skips 138th Street–Grand Concourse. Overnight service makes all stops along the full route, but skips Hoyt Street in both directions. For up to an hour after evening events that are held at Yankee Stadium, a special downtown-only express service runs between 161st Street–Yankee Stadium and Bowling Green.

Until 1983, rush hour 4 trains originated and terminated at Flatbush Avenue–Brooklyn College in Brooklyn.