Boufal has joined Celta on a season-long loan.
After two days of training with Celta, the midfielder was presented to the local media yesterday.
"Celta was long interested in me and I am very happy to be here, I am a fan of the League, playing in it was my dream as a child," said Boufal.
"I really like the offensive game and Celta's way of play."
Celta chief Felipe Minambres also declared: "We are very happy that he has finally reached Celta, we tried for him last year, it was a tough negotiation with Southampton, we have a lot of confidence in him and that in Celta he can show his best football again."