William Silas Pearse (21 May 1838 – 30 December 1908) was an Australian businessman, pastoralist, and politician who served in both houses of the Parliament of Western Australia.

After being educated privately, he went into partnership with his brother (George Pearse), opening a butchery and tannery in Fremantle.

When the trust was converted into a town council in 1871, Pearse was elected Fremantle's first mayor, serving in the position until 1872 (and as a councillor until 1874).

[1] In 1872, Pearse was elected to the Legislative Council as one of two members for the seat of Fremantle, alongside William Marmion.

[2] He was re-elected at the 1894 election, but resigned from parliament in April 1895 in order to take an extended trip to Europe with his family.