The Mexico goalkeeper spent the last season with Granada, on loan from Malaga, and suffered behind a poor back line. The team won just four La Liga matches and was relegated to the second division.
But the 31-year-old will continue on in a top division after making a move to the Belgian side, though Standard won't participate in European competition in the upcoming season after finishing ninth in 2016-17.
During the Confederations Cup, in which he played four games, the former Ajaccio shot-stopper was rumored to make a return to Ligue 1. But late Friday the focus of transfer rumors switched to his final destination.
"Guillermo has a great international experience, whether at the club level, where he played in the Mexican Championship, then in the French Ligue 1 and the Spanish Liga, or in the national team," Olivier Renard, Standard's sporting director, said in a club statement. "He had an excellent World Cup in 2014. Guillermo is ready for a new challenge and will certainly bring a lot to our group."
The deal will be finalized once Ochoa completes medical tests later this week. He'll become the second Mexican to play for the club after Carlos Hermosillo moved there from Club America in 1990. The Mexico legend scored once in five games with Les Rouches.