The 31 year-old moves to LaLiga after having had his contract terminated at Newcastle United by mutual consent in January.
The South Korea international was confirmed as a new Mallorca player and could make his debut in the weekend clash with Getafe.
"It's a great honour to play for Mallorca. For me, it's a great honour to play in Spain because when I was younger I dreamt of playing in Spain so hopefully I’m looking forward to playing against the best players. Dreams do come true," Ki said.
"I think now fans from Korea are going to try and be a bit more interested because I play for the team.
"Take [Takefusa] Kubo is also a very talented player and those from Japan are watching games. Hopefully we will be able to contribute to the team and a lot of fans from the area will support us."
Mallorca is 18th in the table and two points from safety after 25 matches, although four points from its past two games against Deportivo Alaves and Real Betis have given its survival hopes a boost.