Reunion has multiple meanings:

• Réunion is an overseas département and région of France, located in the Indian Ocean, east of Madagascar.
• La Réunion is the name of a commune in the Lot-et-Garonne département in France.
• Reunion is the name of a pop music group best known for their 1974 hit song "Life Is A Rock (But The Radio Rolled Me)", a rapid-fire musical recitation of nearly 100 artists, songs, industry names, and trends in pop music up to that date.
• Re-union is the name of a Dutch duo who performed at the Eurovision Song Contest 2004.

"Reunion" can also mean that a group of people that have been separated reunite, usually but not always in the form of a party. This reference is mostly used in reference to high school and college graduation milestone anniversaries.