After a crazy 17-minute delay, the penalty was finally able to be taken and Diaz, the top scorer in the tournament, attempted a cheeky 'Panenka' that only floated the ball harmlessly into the grateful arms of keeper Edouard Mendy.
Mazraoui has performed with his usual composure and quality, at full-back, but was withdrawn for Hamza Igamane in the 98th minute.
For the winner, Gueye charged forward, bounced off Achraf Hakimi and unleashed a fierce shot beyond Yassine Bounou to stun the home fans and, although Nayef Aguerd hit the bar, there was no way back for Morocco.
Indeed, only a world-class double save by Bounou denied Cherif Ndiaye another goal as Senegal were crowned kings of the continent for the second time in their history.