Father Joseph (Joe) H. Maier, C.Ss. R., (born 31 October 1939) is an American Redemptorist priest who lives and works in the Klong Toey slums of Bangkok, Thailand, where he co-founded the Human Development Foundation (HDF-Mercy Centre) with Sister Maria Chantavarodom in 1973. For over 35 years, he has administered to Bangkok's poorest, providing vulnerable children and families alternatives to and haven from drugs, violence, sex abuse and prostitution in the squatter slums.