L'International des Feux Loto-Québec, also known as the Montreal Fireworks Festival, is the most prestigious and largest fireworks competition in the world. It has been held yearly in La Ronde over the Dolphins lake, since 1985, and is named after its main sponsor, Loto-Québec. 

It hosts an estimated 3 million spectators each year, with approximately 6,000 fireworks set off during each show. Each summer, eight or nine pyrotechnical companies from different countries present a 30-minute-long pyromusical show, competing for the Gold, Silver and Bronze Jupiters or trophies.

The competition takes the form of a series of biweekly fireworks shows usually beginning in late June and ending in late July. The fireworks are synchronized to music which is also broadcast over a provincial radio station.

Spectators can purchase tickets to have reserved seats in La Ronde: they can buy them on site, on-line or through the Admission group to obtain an exceptional view of the lower altitude display and the whole perspective. 

In 2009 and 2010, the shows were held on Saturday nights only, from June to August, however in 2011 shows were again held on Wednesdays and Saturdays beginning end of June until end of July.

According to en.wikipedia