Mother Mary Theodore Williams (born Elizabeth Barbara Williams; February 11, 1868 – July 14, 1931) was an American Black Catholic nun who founded the Franciscan Handmaids of the Most Pure Heart of Mary in 1916. She received her education from the "Ladies of the Sacred Heart" and from the Sisters of the Holy Family. In 1915, while working at Trinity College in Washington, she learned that Father Ignatius Lissner, provincial of the Fathers of the Society of African Missions, needed a religious to found a new community.
A bill proposed in Georgia Legislature threatened to forbid white teachers from instructing black children in public schools and close joint schools founded by Father Lissner, but it never passed. In September 1916, after Father Lissner purchased a house for the new community, Elizabeth arrived (with habit) and soon took vows as Mother Mary Theodore.
The response from both Black and white communities was largely positive, although some white nuns were not supportive due to her race. By 1925, there were sixteen members in her congregation, eventually including women from the West Indies. In 1929, Mother Theodore had the congregation enrolled in the Franciscan family as members of the Third Order.