Alto Paraguay (Spanish pronunciation: [ˈalto paɾaˈɣwaj]; Upper Paraguay) is the least populous as well as a sparsely populated department of Paraguay. The capital is the town of Fuerte Olimpo.

In 1992, the Chaco Department was merged with Alto Paraguay.

Alto Paraguay contains many natural resources, so is home to several national parks, each with different characteristics. The Defensores del Chaco National Park is the largest in the Paraguayan territory and holds the hill Cerro León, the highest point in northern Paraguay. The dry terrain optimally grows various species of cactus. Parque Nacional Río Negro is an area with several small lakes and most of the department's fauna. In the dry regions are Parque Nacional Coronel Cabrera and Parque Nacional Chovoreca.

Paraguay's largest reserves of undeveloped fertile forest and lowest land prices are found in Alto Paraguay. Agriculture and cattle farming have started to make inroads. The fertility of the Chaco's deep sedimentary soils is generally high, except in the westernmost parts, where there are very sandy soils, and in the eastern plain where there are some seasonal wetlands. Annual rainfall is sufficient in the east (around 1200mm), fair in the center (around 900mm) and scarce in the west (around 700mm). A lack of infrastructure and roads is the primary limitation for farmers in the area.

Current agricultural expansion comes at the expense of the area's native forests. During the two decades between 1990 and 2010, Paraguay had one of the highest deforestation rates worldwide. The World Land Trust estimated 2008 deforestation in the Paraguay Chaco was over 200,000 hectares.

The department's most important activity is cattle ranching, extensive in the savannas of the east and intensive on the planted pastures of cleared land. Cultivation of sorghum, sugar cane and (in planning stage as of January 2009, for the arid west) jatropha are very recent developments.

The department is divided into five districts:

1. Bahía Negra
2. Capitán Carmelo Peralta
3. Fuerte Olimpo
4. Puerto Casado
5. Mayor Pablo Lagerenza

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