William Henry was born in Sligo, Ireland, in 1770. He was a carpenter and joiner before joining the London Missionary Society. He married Sarah Maben and together they had four surviving children. In August 1796, they joined a group of missionaries aboard the 'Duff' in sailing for Tahiti. After deciding it was too dangerous, the missionaries continued on to Sydney, Australia aboard the 'Nautilus'. Along with shipmate James Fleet Cover, Henry established three congregations in Sydney, including at Parramatta, Toongabbie and Kissing Point, which later became St Anne's in Ryde.

In 1811, the family returned to Tahiti and Henry was inducted as a minister in a Tahitian church. His wife, Sarah, died in 1812. On a return visit to Sydney in 1813, he remarried, to Ann Shepherd. They went on to have ten children together. They remained in the islands until retiring to Sydney in 1848. William continued to preach at Kissing Point. He died in 1848, and Sarah in 1882.