Planet Ocean Montpellier, Combined aquarium and planetarium in Odysseum district, Montpellier, France.

Planet Ocean Montpellier is an aquarium and planetarium complex in the Odysseum leisure zone. Its broad glazed facade of tall glass panels carries the words "MARE NOSTRUM AQUARIUM" in white capitals on a dark blue section above. Inside, a central basin stands 10 m high and 18 m in diameter, and the site holds 300 species, a 190-seat amphitheatre and the 55-seat Émeraude Café.

The aquarium opened on 15 December 2007 under the name Mare Nostrum, and its extension at Odysseum was inaugurated on 12 April 2011. In January 2017 the metropolis of Montpellier delegated management of the aquarium and the Galilée planetarium to the company Aspro-Ocio. In April 2018 the two merged to form Planet Ocean Montpellier.

The name Mare Nostrum, still spelled in white capitals on the blue facade, is Latin for "our sea" and was the aquarium's name until April 2018, when it merged with the Galilée planetarium. Inside, a 190-seat amphitheatre equipped for videoconferencing hosts talks, and the Émeraude Café seats 55 people within a tropical forest setting.

The location is easily reached by tram line 1 to Odysseum station and remains open daily from 10 AM to 6 PM throughout the year. Plan ahead for busy periods, particularly on weekends and during school breaks.

The central basin reaches 10 metres in height and 18 metres in diameter, making it one of the largest covered tanks in France. The complex also holds a hurricane and ocean-storm simulator and a 190-seat amphitheatre equipped for videoconferencing.