Holders FC Barcelona were drawn with 10-times winners Atletico Madrid in the Copa del Rey semi-finals on Friday while Celta Vigo will play Alaves in the other last-four encounter.
Atletico Madrid host FC Barcelona in the first leg on February 1 with the second leg at the Nou Camp on February 8.
FC Barcelona have won the Cup a record 28 times and have lifted it in the last two seasons under coach Luis Enrique, who said this week his ideal final would be against his former club Celta.
Barca beat Real Sociedad 6-2 on aggregate to advance to the last four while Atletico saw off Eibar 5-2. Alaves beat Alcorcon 2-0 on aggregate and Celta knocked out La Liga leaders Real Madrid 4-3 on aggregate.
Celta have reached the final three times but never won the trophy.
They entertain Basque side Alaves, the 2001 UEFA Cup finalists who are bidding to reach their first King’s Cup final, in the first leg.
The final is on May 27 with the venue still to be determined, although Spanish media reported it will be at Atletico’s Vicente Calderon, which is set to close at the end of the season.