William Woodruff Niles (May 24, 1832 - March 31, 1914) was the third bishop of the Episcopal Diocese of New Hampshire, United States, and served as such from 1870 until his death in 1914.

In 1868 he also became part-time rector of St. John's Episcopal Church in Warehouse Point, Connecticut.

In the 19th Century, it was not uncommon for an Episcopal bishop to serve at the same time as rector of a parish.

Bishop Niles assumed the unpaid rectorship of St. Paul's Church in Concord and continued in both capacities until his death.

[1][2] In 1879, under his leadership, members of the 1875 Episcopal General Convention founded the Holderness School in New Hampshire, where a living hall was named in his honor.