The 22-year-old penned a four-year contract, starting from summer of 2023, with the 2017 European champion.
Hisham is one of Egypt's hottest prospects.
He joined Nimes in 2019, weeks after helping Egypt U-20 team win the World Championship where he was named Most Valuable Player of the tournament.
He played a vital role with the Pharaohs in the 2021 and 2023 World Championships as well as the Olympic Games that saw the Egyptian side finish fourth for the first time of the country's history.
The former Heliopolis player is the second Egyptian to join Montpellier after Mohamed Mamdouh Hashem who helped the French side win the 2017 Champions League before leaving them to join Romanian side Dinamo Bucuresti in 2018.
Montpellier are leading the league table with 27 points on level with PSG.
(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)