Charlton, second from bottom in the 20-team division with only three wins from 19 games, said Reed had left by mutual consent after just eight matches in charge, six of which were defeats.
Pardew, sacked by West Ham on Dec. 11 after a poor run of results, has signed a three-and-a-half year contract. His first game will be a London derby at home to Fulham on Wednesday.
Reed, a former FA technical Director who joined Charlton's coaching staff in 1995, was promoted to head coach in mid-November after Iain Dowie was sacked.
But he failed to spark a revival and the club suffered a humiliating loss in the League Cup quarter-finals last Tuesday when they were beaten 1-0 at home by fourth division side Wycombe Wanderers.
Charlton said they would make no further comment on the appointment but would hold a press conference on Tuesday.
Pardew's tenure after three years in charge at Upton Park came to an end with last season's beaten FA Cup finalists struggling at the wrong end of the standings. Former Charlton manager Alan Curbishley took over.