The Isthmian League (/ˈɪs(θ)miən/) is a regional football league covering Greater London, East and South East England, featuring mostly semi-professional clubs.

Therefore, a meeting took place between representatives of Casuals, Civil Service, Clapton, Ealing Association, Ilford and London Caledonians to discuss the creation of a strong amateur league.

All the clubs supported the idea and the Isthmian League was born on 7 March 1905.

In 1962 an 'all-star' team from the Isthmian League entered the 1962 Ugandan Independence Tournament, drawing both their games versus Kenya and Ghana.

The reward of promotion into the Conference means that, since 1985, no team has won the league champions title two seasons in succession (as had happened on 22 occasions previously).

In May 2017, The Football Association chose the Isthmian League to add a third regional division at Step 4 as part of further restructuring in the National League System, reducing all divisions at Step 4 to 20 teams.

The sponsors after Rothmans to the present day have been: Michael Lawrie (1977–78), Berger (1978–82), Servowarm (1982–85), Vauxhall-Opel (1985–90), Vauxhall (1990–91), Diadora (1991–95), ICIS (1995–97), Ryman (1997–2017),[2] Bostik (2017–19)[3] and BetVictor (2019–20).

[5] Ryman chairman Theo Paphitis added to his league sponsorship through his flagship companies.

Becoming the longest running sports sponsorship in UK football, Ryman stepped down as sponsors at the end of the 2016–17 season after 20 years.

In its earlier years, the Football League didn't directly promote teams from the Non-League system on merit; instead, holding regular elections, for which any Non-League side could apply to enter.

In practice, only the most ambitious non-League sides put themselves forward for election,[7] and success was uncommon (outside of divisional expansions, from 1945 to its abolition in 1987, only seven clubs were successful in vying for admission to the League).

[7] The first ex-Isthmian League team to reach the Football League was Wimbledon in 1977, followed subsequently by Maidstone United (1989), Wycombe Wanderers (1993), Yeovil Town (2003), Dagenham & Redbridge (2007), Aldershot Town (2008), Stevenage (2010), and AFC Wimbledon (2011).