William Thomas Mercer

The Hong Kong Executive Council in 1860, showing William Mercer (first on left) and Governor Hercules Robinson (in tophat)

William Thomas Mercer (Chinese: 孖沙; Sidney Lau: Ma1 Sa1) (17 October 1821 – 23 May 1879) was a British colonial administrator who served in Hong Kong from 1844 to 1866.