The 23-year-old defender has become the second Dutch arrival at the Liberty Stadium in as many days after Leroy Fer, signing a three-year deal at the south Wales club.
Mike van der Hoorn has completed his move to Swansea City from Ajax, the Premier League club has confirmed.
The 23-year-old defender joins for an undisclosed fee after agreeing terms on a three-year contract.
Van der Hoorn is the second Dutch arrival at the Liberty Stadium in as many days after Leroy Fer made his move from Queens Park Rangers permanent following a loan spell at the end of last season.