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).

In 2003, Chan claimed the name of "Tsuen Wan Election Union [zh]" headed by Albert Chan to take part in the District Council election, and renewed the seat successfully.

In 2004, he joined Hong Kong Democratic Party and partnered with Lee Wing-tat, the former chairman of the Democratic Party to participate in the 2004 Hong Kong legislative election, but failed to enter the Legislative Council.

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.