The 28-year-old, who can play at either centre back or right back, has signed a three-year contract and leaves Ajax after more than 200 appearances since his debut in 2012.
"He has terrific experience from his time with Ajax, including the Champions League and, of course, with the Dutch national team," Brighton manager Graham Potter said on the clubâ€™s website.
"He is really looking forward to the challenge of playing in the Premier League and weâ€™re delighted he is now a Brighton player and weâ€™re looking forward to working with him."
The defender is the second signing announced by the club this week after the arrival of former Liverpool midfielder Adam Lallana as a free agent.
(Reporting by Nick Said; Editing by Toby Davis)