The 2015 S.League was the 20th season since the establishment of the S.League, the top-flight Singaporean professional league for association football clubs.

The league was also known as the Great Eastern Yeo's S.League due to sponsorship reasons.

Tanjong Pagar United withdrew from the league due to financial problems, while Woodlands Wellington merged into Hougang United.

Albirex Niigata (S), DPMM FC and Harimau Muda are invited foreign clubs from Japan, Brunei and Malaysia respectively.

Note: Flags indicate national team as has been defined under FIFA eligibility rules.