Robert Blashel Thompson (October 1, 1811 – August 27, 1841) was an associate of Joseph Smith, Jr., a Danite and leader in the Latter-day Saint movement, and an official historian of the Church of Jesus Christ of Latter-day Saints.
Thompson was born in Great Driffield, in the East Riding of Yorkshire, England. He joined the Methodists at an early age and participated in preaching in Yorkshire. In 1834, Thompson emigrated to Upper Canada and settled in Toronto. In May 1836, he was baptized a member of The Church of Jesus Christ of Latter-day Saints by Parley P. Pratt, a missionary who was preaching in Toronto. On July 22, 1836, Thompson was ordained an elder in the church by John Taylor.
Thompson moved to Kirtland, Ohio, where the majority of Latter-day Saints were gathering. He married Mercy Rachel Fielding in Kirtland on June 4, 1837. Later that month, the couple traveled to Upper Canada as missionaries for the church. They returned to Kirtland in March 1838.
In 1839, the Thompsons attempted to settle in Missouri with a large number of other Latter Day Saints. While in Missouri, Thompson was a Danite and participated in the 1838 Mormon War. He was standing next to Apostle David W. Patten when Patten was killed at the Battle of Crooked River.