Reserve team coach Luis Castro will take over on an interim basis, the former European champions said, following the sixth coaching change of the season in the Portuguese league.
Porto lost a 5-1/2 year unbeaten home league record when they were beaten 1-0 by Estoril 10 days ago and then squandered a two-goal lead in a match that finished 2-2 at Guimaraes.
They were also knocked out in the Champions League group stage, although they have reached the last 16 of the Europa League, where they face Napoli, after an away goals win over Eintracht Frankfurt.
Fonseca, who last season led modest Pacos de Ferreira into the Champions League playoff round, was Porto's eighth coach in 10 seasons since the departure of Jose Mourinho who won the UEFA Cup and Champions League with the club.)
- Sports & Recreation