Sirena Airport (ICAO: MRSN) is a small, unpaved airstrip located within Corcovado National Park on the Osa Peninsula in southwestern Costa Rica. It serves as a critical access point for researchers, park rangers, and ecotourists visiting the remote Sirena Biological Station, one of the most biodiverse regions on Earth. The airstrip is not served by commercial scheduled airline service but accommodates small charter aircraft and light planes operated by regional air taxi companies. Due to the jungle environment and basic infrastructure, operations are highly weather-dependent and flights must be carefully coordinated with park authorities. The surrounding area is accessible only by air or by multi-day hiking or boat travel, making the airstrip an essential logistical link for those working in or visiting Corcovado's interior. No passenger terminal facilities exist in the conventional sense.