Maicuru Biological Reserve, biological reserve in Almeirim and Monte Alegre, Pará, Brazil

Maicuru Biological Reserve is a large protected area in Pará state, Brazil, covering more than 11,500 square kilometers of rainforest and bordered by the Maicuru and Jari rivers. The landscape features dense tall trees, approximately 3,700 kilometers of rivers and streams, and submontane rainforest with multiple vegetation layers.

The reserve was established in 2006 to protect the natural environment and preserve endangered species found only in this region. Its remote location and limited human access over the years helped keep ecosystems largely intact and functioning.

The reserve lies in the Center of Guiana Endemism, a biogeographic zone spanning parts of Brazil, Venezuela, Guyana, French Guiana and Suriname. Its management council was formed on 6–7 March 2013 alongside that of the Grão Pará Ecological Station. The reserve is bordered by the Tumucumaque Indigenous Park and the Rio Paru d'Este Indigenous Territory.

Access to the reserve is limited and requires special permission from the managing agency, with most visitors arriving by small airplane that lands at strips near mining sites. Visits are restricted to research or educational purposes only, and all activities must follow strict conservation rules.

The reserve lies in the Center of Guiana Endemism, a belt of species ranges spanning parts of Brazil, Venezuela, Guyana, French Guiana and Suriname. Its managers describe it as a "mega reserve", sized to hold a complete sample of species with room to persist over generations. The 2011 management plan was prepared by Conservation International with the Museu Paraense Emílio Goeldi.