The 2020–21 season was the 106th season of the Isthmian League, which is an English football competition featuring semi-professional and amateur clubs from London, East and South East England. The league operates four divisions, the Premier Division at Step 3, and three divisions, North, South Central and South East at Step 4 of the National League System. This was the third season since the former South Division was subdivided into the South Central and South East divisions. The league is also known as the Pitching In League under a sponsorship deal with Entain, formerly GVC Holdings.