Leo Sauer (born 16 December 2005) is a Slovakian professional footballer who plays as a winger for Feyenoord and the Slovakia national team.

Sauer started his football career with Slovan Bratislava. In the summer of 2018 he moved to the youth academy MSK Zilina. Sauer made his debut in the Slovakian 2. Liga for Zilina B on 27 February 2022 against FC Petrzalka.

Sauer joined Feyenoord initially on loan from MSK Zilina in 2022, but in April 2023 signed a three-year professional contract with the Dutch club. On 20 August 2023, Sauer made his debut for the club in an away match against Sparta Rotterdam by coming in at half-time, scoring the 2–2 in the added time to secure a point for the club.

Sauer played for the Slovakia U-19 side alongside his older brother, Mario Sauer. Both were selected for the Slovakia U-20 side to compete at the 2023 FIFA U-20 World Cup.

On 5 October 2023, at the age of only 17, coach Francesco Calzona called him to the Slovak senior national team. On 26 March 2024, Sauer became the youngest ever player to play for the national team after coming on as a substitute in a friendly against Norway.