The NYPD is seeking the public's help in identifying a lewd man who exposed himself on the D train in Brooklyn, authorities said.

A straphanger took this picture of the subway rider touching himself shortly before 4:35 p.m. Aug. 15 at the Bay Parkway subway station, cops said.

The lewd man was wearing a black v-neck T-shirt, as well as black pants and sneakers.

Tipsters are asked to call 1.800.577.8477, or visit the Crime Stoppers website at nypdcrimestoppers.com. All calls will be kept confidential, police added.