The 2021 Manly-Warringah Sea Eagles Season was the 72nd in the club's history since their entry into the then New South Wales Rugby League premiership in 1947.

Source:[2] Manly had one of their worst start to a season in club history, losing all of their first four games and at a combined score of 156–34.

[7] The following week, Manly produced one of the biggest comebacks in history against the Gold Coast Titans after being down 24–8, the team scored 48 unanswered points to win 56–24.

The game also saw a collective effort from Reuben Garrick, Daly Cherry-Evans and Tom Trbojevic to score the try of the year.

[13][14][15] Manly started off with a poor performance to begin the finals, losing to the Melbourne Storm 40–12 at Sunshine Coast Stadium forcing them into a second chance semi due to them finishing in the top four.

[17] On the lead up to their preliminary final match against the South Sydney Rabbitohs, many people, especially former Penrith player Ryan Girdler criticised Manly for making the top four but not beating any side that finished in the top four labelling them as 'flat track bullies' stating that they don't deserve to be 80 minutes away from a grand final.

[18] Manly went on to lose the match 36–16, with Tom Trbojevic breaking Phil Blake's record (27) for most tries in a season for the club scoring 28.