The 24-year-old Brazilian had been heavily linked with a move to Stamford Bridge, but he has elected to stay in Ukraine and join the league leaders.
Taison's form for his club caught the eye of a host of clubs across Europe, including defending UEFA Champions League winner Chelsea. Te Donbass Arena outfit have now pounced for the 24-year-old, activating his release clause.
"On January 10, the presidents of Shakhtar and Metalist negotiated the transfer of Taison from the Kharkiv club to the Donetsk team," a statement on the club's official site read. "Shakhtar paid $20 million, and we got a player who really wanted to join our team. The Brazilian player's five-year contract started on January 11."
The attacker moved to Metalist from Internacional in 2010, and he made 57 league appearances for the club, scoring 13 goals. Shakhtar has enjoyed a fantastic Ukrainian Premier League season thus far and currently sits 13 points clear of Dnipro in the table, having won 17 of its 18 games.
The club faces Borussia Dortmund in the last 16 of the Champions League and adds Tiason to the likes of attacking stars Willian, Fernandinho and Henrik Mkhitaryan.