The 47-year-old was widely reported to have reached an agreement with Ahly in recent weeks, with the official unveiling taking place on Thursday.
The Spaniard began his managerial career in January 2019 with Inter Turku in Finland before moving to South Africa to take charge of Orlando Pirates in July 2022.
Though he failed to break Mamelodi Sundowns' domestic dominance in the league—ongoing since the 2017/18 season—Riveiro led the Pirates to three MTN8 Cup titles (2022/23, 2023/24, 2024/25) and two Nedbank Cup triumphs (2022/23 and 2023/24).
He also faced Ahly twice in the 2025 CAF Champions League group stage, overseeing a 0-0 draw in Johannesburg before securing a surprise 2-1 win at Cairo Stadium.
Both clubs advanced to the quarter-finals.
Interim coach Emad El-Nahass, who guided Ahly to the league title following the departure of Swiss manager Marcel Koller, will remain part of the technical staff under Riveiro.
Riveiro is set to begin his new role on Friday as Ahly prepare for the FIFA Club World Cup, which kicks off on Sunday, June 15 in the United States.
Ahly have been drawn in Group A alongside MLS side Inter Miami, Brazilian outfit Palmeiras, and Portuguese champions FC Porto.
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