Amir Khan has agreed to face undefeated WBO world welterweight champion Terence Crawford in the US on 20 April.
Khan, 32, returned to boxing last April after 23 months away from the sport and secured two wins in 2018.
The Briton had an offer to face domestic rival Kell Brook in a bout, which his team had said would prove more financially rewarding.
But he will instead be a heavy underdog against 31-year-old Crawford, who has held world titles in three divisions.