Björn Markus Seeliger (born 11 January 2000) is a Swedish swimmer. He was a junior champion in 50 m freestyle at the 2018 European Junior Swimming Championships and holds the Swedish record for 50 m backstroke. He was part of the Swedish team that won 4 × 100 m mixed relays at the 2019 FINA Swimming World Cup meet held in Berlin. He competed in the men's 100 metre freestyle event at the 2020 European Aquatics Championships, in Budapest, Hungary.
In Sweden, Seeliger represented Södertälje SS before he represented Stockholms KK.