The 2018 European Champions Cup final will be staged at Bilbao's San Mames Stadium, which will also play host to the Challenge Cup showpiece.
European Professional Club Rugby (EPCR) announced on Monday that the 53,289-capacity Spanish venue would stage the two finals, which take place over one weekend.
San Mames, which has recently undergone redevelopment, is also a host venue for Euro 2020. Newcastle in England has been awarded the 2019 finals.
Spain has hosted high-profile rugby union clashes before, with the 2016 Top 14 final between Toulon and Racing 92 having been played in front of a crowd of over 99,124 at Barcelona's Camp Nou - a record for a club match.
EPCR chairman Simon Halliday, who alluded to the fact that Champions Cup matches have been staged in San Sebastian before, said: "We are very excited to be taking the best club rugby in the world to fans in what is largely a new market.
"Bilbao is an excellent destination which breaks new ground for our tournaments and we see this as a big step in the expansion of our sport across the continent.
"Fans have previously flocked to matches in Spain both in the European Cup and for last season's Top 14 final and they will be sure of a unique, atmospheric weekend in 2018.
"Newcastle's commitment to the bid also made it an easy decision to award them the finals in 2019, building on their significant experience of staging major sporting occasions including Rugby World Cup 2015 matches."
This year's Champions Cup has reached the semi-final stage, with Clermont to face Leinster and Munster taking on reigning champions Saracens.