William Derby Johnson Jr. (1850-1923) was a Latter-day Saint polygamist, bishop, school administrator, doctor, and colonizer in Mexico.

William Derby Johnson Jr. was born on May 2, 1850, in Council Bluffs, Iowa, to parents Jane Cadwallader Brown and William Derby Johnson Sr. Johnson spent the first ten years of his life living in Council Bluffs, Iowa, and Winter Quarters, Nebraska. In 1860, he crossed the plains with his parents and spent the next ten years of his life in Salt Lake City, Utah. During these years, Johnson served as a volunteer for the Black Hawk War in Sanpete County, Utah and he studied at Deseret University (now University of Utah) where he received a diploma in bookkeeping and accounting.

It was also while living in Salt Lake City that Johnson met and married his first wife, Lucy Annie Salisbury, in 1869. They had one son together. During their marriage, William and his family moved to an area fifteen miles east of Kanab, Utah, where they settled the town of Johnson. He taught school in Kanab and participated in John Wesley Powell's explorations of the Colorado River. They lived in Johnson until 1885. William also married three more wives: Lucy Elizabeth Brown (1877), Charlesetta Prescott Cram (1879), and Mary Agnes Riggs (1884).

In 1885, Latter-day Saint Apostle Erastus Snow recommended that Johnson take his families to Mexico in order to escape persecution for practicing polygamy. It was while making arrangements for his wives and families to follow him to Mexico that Johnson learned of the death of his first wife, Lucy Salisbury (in later years he would also suffer the death of their only son). He eventually settled Colonia Diaz in Chihuahua, Mexico where he served as bishop until 1911. He also acted as a doctor for the Mexican people and had a high profile career as Superintendent of Church schools for The Church of Jesus Christ of Latter-day Saints.

Johnson died on October 17, 1923 in Tucson, Arizona.