is an American professional soccer player who plays as a goalkeeper for Major League Soccer club Colorado Rapids and the United States national team.

Steffen began his youth career with West Chester United before joining the Philadelphia Union in 2012. In May 2013, Steffen committed to playing college soccer for the Maryland Terrapins. He established himself as the starting goalkeeper, spending two seasons with the Terrapins before joining German club SC Freiburg, being assigned to play with the reserves. In July 2016, Steffen returned to the United States with the Columbus Crew, joining United Soccer League club Pittsburgh Riverhounds on loan the following month. From the next season, Steffen would establish himself as the starting goalkeeper for the Columbus Crew, winning the Goalkeeper of the Year Award in 2018.

In December 2018, Steffen agreed to join Premier League club Manchester City. He signed in July 2019 before immediately being loaned to Bundesliga side Fortuna Düsseldorf for the 2019–20 season. He was the starting goalkeeper but was then sidelined for the remainder of the loan due to injuries. He returned to Manchester City the following season, serving as a backup to Ederson. In April 2021, Steffen won his first career trophy, starting in the final of the EFL Cup; he kept a clean sheet as Manchester City beat Tottenham Hotspur 1–0. In January 2024, Steffen agreed to leave Manchester City and returned to Major League Soccer for the first time since 2018, signing with the Colorado Rapids.

Steffen had represented the United States youth teams before being called into the senior squad in May 2016. He made his senior debut in January 2018 against Bosnia and Herzegovina. He was the starting goalkeeper for the United States during the 2019 CONCACAF Gold Cup, leading the side into the final where they were defeated 1–0 by Mexico. He then served as backup to Brad Guzan through the Nations League but then became the starting keeper in the finals. Steffen started the final against Mexico but was substituted in the 69th minute by Ethan Horvath after suffering a knee injury. The United States would go on to win 3–2 in extra time, earning Steffen his first international honor.