Singapore Democratic Alliance

The Singapore Democratic Alliance (abbrev: SDA; Chinese: 新加坡民主联盟) is an alliance of political parties in Singapore. The SDA was formed shortly before the 2001 general election to provide a common grouping under which different opposition parties could stand as a united front in elections against the ruling People's Action Party (PAP). The founding Chairman of the SDA was the leader of the Singapore People's Party and former Member of Parliament (MP) for Potong Pasir, Chiam See Tong.

The SDA was initially an alliance of four political parties: the National Solidarity Party (NSP), the Singapore Justice Party (SJP), the Singapore People's Party (SPP), and the Singapore Malay National Organisation (PKMS).

In 2007, the National Solidarity Party withdrew from the alliance. In February 2011, the SDA's Council voted to relieve Chiam of his role as Chairman, following which Chiam announced that the Singapore People's Party was withdrawing from the SDA.