Isla de Janitzio (Spanish pronunciation: [xaˈnitsjo]) is the largest of five islands in Lake Pátzcuaro in the state of Michoacán, Mexico.

The town of Janitzio, which means "maize flower" in Purépecha, is located atop a hill on the island. Janitzio can only be reached by boats which run regularly back and forth from about 7:30 am to 6 pm, accessible from Pátzcuaro's pier (embarcadero). The boats take approximately 25 minutes to reach the island. These boats can be hired to take visitors around other parts of the lake.

The town is known for the butterfly fishermen who are skilled at lowering their butterfly-shaped nets to catch "pescado blanco" (Chirostoma estor), a species of freshwater silverside endemic to the lake which is important to the local cuisine. These fisherman were at one time depicted on the reverse of the 50 peso banknote. This banknote is now a valuable collector's item.

The island is the subject of Silvestre Revueltas's 1933 composition Janitzio.