Alaves managed to secure promotion from Spain's Segunda Division after beating Numancia 2-0 thanks to goals from Manu Garcia and Raul Garcia.
Next season will see the Basque club play in Spain's top flight for the first time in 10 years.
Leganes look set to join Alaves in the top flight next season, with the team sitting in second place with one match remaining. However, Gimnastic Tarragona are just a point behind in third, but have to face the promoted Alaves, whilst Leganes will play 14th place Mirandes.