Bas Jan Ader, Dutch-American photographer and director (d. 1975)

Bastiaan Johan Christiaan "Bas Jan" Ader (19 April 1942 – disappeared 1975) was a Dutch conceptual and performance artist, and photographer. His work was in many instances presented as photographs and film of his performances. He made performative installations, including Please Don't Leave Me (1969).

Ader was lost at sea in 1975, attempting to cross the Atlantic Ocean from the American coast to England sailing in a thirteen-foot sailboat. His deserted vessel was found off the coast of Ireland on 18 April 1976, offering few clues as to his fate.