The Women's Super League champions produced a clinical display to add the prestigious cup trophy to their league title, with star performers Khadija Shaw and Alex Greenwood leading the charge in a one-sided contest.
Shaw, who claimed the WSL Golden Boot for a third consecutive season, once again demonstrated her importance to City's success by breaking the deadlock in the first half. The prolific Jamaican striker continued her outstanding campaign with a composed finish that settled any early nerves for Gareth Taylor's side.
City doubled their advantage shortly afterwards through Greenwood, whose superbly struck free-kick left Brighton's goalkeeper with no chance. The England defender's effort highlighted City's dominance as they took firm control of the final before the interval.
Brighton, appearing in one of the biggest matches in the club's history and chasing a first major trophy, struggled to match City's quality and experience. Despite showing determination, they found it difficult to create meaningful opportunities against a well-organised City defence.
The introduction of fresh legs in the second half further tilted the contest in City's favour. Substitute Aoba Fujino extended the lead with a well-taken finish before fellow replacement Vivianne Miedema added a fourth goal to put the result beyond any doubt.
The convincing victory underlined Manchester City's status as the dominant force in English women's football this season, completing a memorable domestic double and ending the campaign on a high note.
For Brighton, the defeat was a disappointing end to an otherwise impressive cup run. While they fell short in their bid to claim a historic first major honour, reaching the Wembley final marked another significant step forward for the club.
Meanwhile, City's celebrations continued long after the final whistle as Shaw, Greenwood and their teammates lifted the FA Cup in front of a jubilant crowd, capping a season that will be remembered as one of the finest in the club's history.