Alexander Hack (born 8 September 1993) is a German footballer who plays as a centre-back for FSV Mainz 05 II. At international level, he made four appearances for the Germany U20 national team.
Hack joined Mainz 05's reserve team from SpVgg Unterhaching in 2014 and became a regular starter.
He made his first-team debut in the Bundesliga in the first half of the 2015–2016 season in a 3–1 win against Eintracht Frankfurt.
In June 2017, Hack agreed a contract extension until 2022 with Mainz.