The 24-year-old is equally adept on either flank and will provide competition at wing-back in Nuno Espirito Santo's preferred 3-4-3 system.
Otto was a consistent presence in the Celta team last season, missing just two La Liga games over the course of the campaign.
Jonny came through the youth ranks at Celta and progressed to the first team, making over 200 senior appearances for the club.
A Spain U21 international, Jonny is highly-rated in his homeland and will no doubt be relishing the chance to broaden his horizons with a spell in English football.
Jonny's arrival could open the door for Barry Douglas to make a permanent switch to Leeds United.
The defender joins Benik Afobe, Willy Boly, Rui Patricio, Leo Bonatini, Raul Jimenez, Diogo Jota, Ruben Vinagre and Joao Moutinho in joining the club this summer.
July 25, 2018