Sumly Chan Yuen-sum (born 23 March 1958 in Hong Kong) is a social worker and politician in Hong Kong, a member of the Civic Party, the chairman and the member of Tsuen Wan District Council (Lei Muk Shue East). He has served as district councillor in Tsuen Wan since 1985 and is one of the Hong Kong district councillors with the longest years of service.
In November 2007, he succeeded in keeping the seat of the district council. In 2008, Fernando Cheung and Chan represented Civic Party to participate in the 2008 Hong Kong legislative election, but both Cheung and he lost.
In 2016, he was nominated by Civic Party to run for the District Council (Second) constituency. He spent plenty of time in finding his 15 nominees (they must be a district councillor) which caused him to start his campaign later than others. As a result, he was constantly ranked either sixth or seventh in the rolling poll which caused him to suspend his campaign on 2 September 2016 in order to have at least three pan-democrats to take the District Council (Second) seat. Leung Yiu-chung, who was then elected in the District Council (Second) election was somehow actually helped by Sumly. Sumly was meant to have 16 nominees with him. However, one of them is duplicated with Leung. Therefore, Sumly decided to forfeit it in order to let Leung enter the race.[1]