Stefan Ilsanker (born 18 May 1989) is an Austrian professional footballer who plays as a defensive midfielder for German club Eintracht Frankfurt. He has represented his country at Under 19 European Championship and was a member of the under-21 team. Ilsanker has been a full senior international since 2014.
Ilsanker began his career in the youth squad of 1. Halleiner SK as goalkeeper but soon switched into the midfield. In 2005, he signed with Red Bull Salzburg, where he played in the Red Bull Juniors team.
On 4 April 2009, Ilsanker was called up to the first team bench for a league game. His first game for Red Bull Salzburg was a national cup match on 15 August 2009. On 25 August 2009, he played his first international game for Red Bull Salzburg in the UEFA Champions League qualifier versus Maccabi Haifa.
At the end of the 2009–10 season Ilsanker signed with SV Mattersburg. In 2012, he came back to Red Bull Salzburg. In the meantime, he was a regular of the starting team of the club. On 26 February, the club announced, that his contract was extended till 2018.
Stefan Ilsanker was sent-off on 19 December 2018 against Bayern Munich.
On 31 January 2020, Ilsanker joined Eintracht Frankfurt on a deal lasting until 2022. On 3 June 2020, Ilsanker came off the bench against SV Werder Bremen and scored twice in the final 10 minutes of the match to secure a 3–0 victory.