63 Seaworld, Public aquarium in Yeouido district, Seoul, South Korea.

63 Seaworld is a public aquarium located in the 63 Building in Yeouido, featuring more than 400 marine species across multiple floors in glass-walled displays. The space is organized into different zones that represent various ocean habitats and their inhabitants.

Opened on 27 July 1985 in the basement levels of the 63 Building, it was the first public aquarium in South Korea. It closed for renovation on 1 September 2015, with 16 billion won invested, and reopened as Aqua Planet 63 on 1 July 2016. It shut permanently on 30 June 2024 and was demolished on 3 July 2024.

The aquarium's stated mission was to be an education center about marine life, and it reproduced ocean habitats from around the world. Its harbor seal show began in 1990 and ran daily, with two of four seals performing four times a day.

The aquarium occupied the first basement level of the 63 Building in Yeouido, Seoul, with two more basement levels used for exhibits; the third basement was an equipment level closed to the public. The site is near Yeouido Station on Seoul Subway Line 5 and Line 9. The facility permanently closed on June 24, 2024, and was demolished on July 3, 2024, so the space is no longer open to visitors.

The 63 Building was the tallest building in Korea when it was completed, and the aquarium's three basement levels covered 5,630 square metres. The migratory tank, 2.1 metres high and 42 metres around, was made of 11-centimetre-thick acrylic.