Athletic Bilbao will be searching for a new head coach ahead of next season after Marcelino confirmed he is leaving the club.
Marcelino took over at the Basque club on January 3, 2021. He took Athletic to the Supercopa de Espana title later that month.
Athletic also made the final of the 2021-22 edition of the tournament but lost to Real Madrid, while former Villarreal and Valencia coach Marcelino oversaw two Copa del Rey final defeats – one of which was delayed from the 2019-20 season due to the coronavirus pandemic.
Marcelino's side made the semi-finals of this season's Copa, beating both Barcelona and Madrid, but they lost over two legs to Valencia, who were beaten by Real Betis in the final.
The 56-year-old's contract expires at the end of June and will not be renewed. He took Athletic to eighth in LaLiga in the 2021-22 season, following on from a 10th-placed finish in the previous campaign.
Marcelino oversaw 59 league games in total, winning 19 (32.2 per cent) and losing 17, with his team scoring 70 goals while conceding 59 in return, averaging 1.36 points per game.
Marcelino told a news conference on Tuesday: "We believe the time has come to step aside and bring an end to a beautiful story. We're proud to have had the privilege of coaching Athletic Club.
"Thank you to everyone, I wish you all the success in the future. This is not a goodbye. You will always be in our hearts. Always.
"Thank you, from the bottom of my heart, to the fans. We were orphans while the pandemic attacked us. Then I found out what it really means to be at San Mames as Athletic's coach.
"We have had some magical nights and unforgettable moments."
Athletic, who lost 1-0 to Sevilla in their final game of the season, have been linked with Mauricio Pochettino, should the former Tottenham boss be dismissed by Paris Saint-Germain.