Joseph Gillespie Armstrong (October 15, 1901 - April 23, 1964) was an American suffragan bishop of the Episcopal Diocese of Pennsylvania from 1949 until November 7, 1960, when he was elected coadjutor. He succeeded Rt. Rev. Oliver J. Hart as Bishop of Pennsylvania when Bishop Hart retired on July 19, 1963. However Bishop Armstrong's diocesan episcopate only lasted nine months before his death.