Petrel Lagoon (Spanish: Laguna de Petrel or Laguna Petrel) is a coastal lagoon located in Pichilemu beach, Chile, in front of Pichilemu railway station.

It contains a high percentage of sea water, and it was formerly one of the main attractions of Pichilemu.

It is named after the hacienda San Antonio de Petrel, located nearby Pichilemu.