Sociedade União 1º Dezembro is a sports club from Sintra, Portugal.

[1] The women's football team played in the top national league, the Campeonato Nacional de Futebol Feminino and were the dominant force during the 2000s.

[2] The women's football section of the Sociedade União 1º de Dezembro was created in 1995, making the club one of the few in Portugal to have both a men's and a women's football team.

Ever since the creation of the section, the team have won 12 league titles – 11 of which in a row – and 7 Portuguese Cups making it the most successful women's football team in Portugal.

The section also managed an U-18 women's football team which disputed the Campeonato de Promoção de Futebol Feminino, the name of the women's football second division.