The Rev. Fred Shuttlesworth is being treated at a Birmingham hospital for pneumonia and dehydration.
The 86-year-old Shuttlesworth was placed in the intensive care unit at St. Vincent's Hospital on Sunday, according to his wife, Sephira Shuttlesworth.
He was listed in stable condition.
Shuttlesworth, a civil rights pioneer, helped to lead the fight against segregation in Birmingham in the 1950s and 60s.