Millwall have been depicted in films several times, specifically highlighting the club's hooliganism firm the Bushwackers and the rivalry with West Ham United.[150] Often glorifying football violence in the beginning, each film typically ends in loss of life, showing the futility of hooliganism.[180]

Millwall, who had now also dropped 'Athletic' from its name, were invited to join the Football League in 1920 for the 1920–21 season, along with 22 other clubs, through the creation of the new Football League Third Division.[13] The Southern League was shorn of its status, with almost all its clubs deciding to leave—Millwall followed suit.[13] Millwall's first Football League match was on 28 August 1920 at The Den, and they were 2–0 winners against Bristol Rovers.[14]

Based on all results during the club's 89 seasons in the Football League from 1920–21 to 2015–16, Millwall are ranked as the 39th most successful club in English football.[131] The following table details the club's major achievements:

Join the European football family today! Get involved with games, competitions and much more.

Millwall were listed eighth out of a list of 92 Football League clubs with the most rivals, with West Ham United, Crystal Palace, Charlton Athletic, Leeds United, Portsmouth and Gillingham considering them a major rival.[105][106]

Millwall players inducted into the English Football Hall of Fame:[119]

During the late 1950s and early 1960s Millwall's form was poor, and they were relegated into (and became a founding member of) Division Four.[24] The first time in their history they had competed in the fourth tier of English football, which they remained in for four seasons until 1962. They returned for the 1964–65 season, but were immediately promoted. This is the last time Millwall played in the fourth tier.[25]

On 7 April 1945, Millwall appeared in a Football League War Cup final at Wembley Stadium against Chelsea, but because it was a wartime cup final it is not acknowledged in the record books.[21] With the war in Europe in its last days, the number of spectators allowed to attend games was relaxed. The attendance was 90,000, the largest crowd Millwall have ever played in front of, which included King George VI, whom the team were introduced to before kick-off.[22]

The following is a list of notable footballers who have played for Millwall, including players who have been honoured in Millwall's Hall of Fame and have significantly contributed to the club's history[5][121] be it through being founder member players, having been given a testimonial for 10 years of service at the club, making over 100 appearances, scoring over 50 goals or having received recognition by their country in the form of international caps while playing for the club.[122][123][124]

Other songs that have been regularly played at The Den over the years in the build-up to a game include "London Calling" by The Clash, "No Surrender" by Bruce Springsteen, "Town Called Malice" by The Jam and "House of Fun" by Madness, which features the lyric "welcome to the lion's den...". Status Quo's cover version of "Rockin' All Over the World" is played after every home win.[104]