Tenorio Volcano National Park, Protected rainforest and volcano area in Guanacaste Province, Costa Rica.

Tenorio Volcano National Park is a protected area in the Cordillera de Guanacaste, Costa Rica, covering 18,402.51 hectares of premontane rain forest and cloud forest. Its massif comprises five main craters, and the inactive Tenorio volcano rises to 1,916 m. The 3 km Sendero del Tenorio leads to the 20 m Rio Celeste waterfall, a viewpoint over the volcanic complex, and the Los Teñideros confluence.

The park was created in 1995 by executive decree No. 24240-MIRENEM, covering 18,402.51 hectares of forest and volcanic terrain in the Guanacaste mountain range. It belongs to the Arenal-Tempisque Conservation Area, managed by Costa Rica's National System of Conservation Areas. The Tenorio massif, with five main craters, is considered inactive; reports of an eruption in 1814-1816 are unconfirmed.

The name Rio Celeste comes from the river's light-blue tint, produced where the Buenavista and Quebrada Agria streams meet at a spot called Los Teñideros. The park's main trail, Senderos del Tenorio, is 3 km long and ends at Los Teñideros and Los Hervideros, where water temperatures reach 31 to 94 °C. Nearby stands the El Pilón biological station, which sleeps 25 people.

The park is open during daylight hours and visitors should prepare for wet conditions since rain is frequent and trails can become slippery. Sturdy footwear and water-resistant clothing are recommended to stay safe and comfortable while exploring the area.

The blue of the Rio Celeste comes from Mie scattering of light by colloidal aluminosilicate particles. The colour appears where the volcanic Rio Buenavista meets the acidic Quebrada Agria at Los Teñideros, and the particles aggregate. The river then drops about 20 m at the Celeste waterfall.