Khosrov Forest State Reserve is a nature reserve in Ararat Province of Armenia.

The reserve is one of the oldest protected areas in the world having a history of about 1700 years. It was founded in the 4th century (334–338) by the order of Khosrov Kotak, King of Armenia who gave it his name. It was founded to improve the natural climatic conditions of adjacent territories of Artashat – the capital city of Armenia of the given period and the newly established city of Dvin to ensure conservation and enrichment of flora and fauna species; serve as a ground for royal hunting, military exercises and entertainments.

This area was designated as a state reserve in September 1958 and covers around 23213.5 ha at elevations from 700 to 2800 m above sea level. The Khosrov reserve protects juniper (Juniperus polycarpos) and oak (Quercus macranthera) forests from Tertiary Period, arid associations of semi-desert and phrygana landscapes and other Mediterranean relict plant ecosystems as well as the genetic fund of rare animals and plants adapted to the reserve conditions. It also includes wetlands of international importance. Khosrov Forest State Reserve, thanks to its numerous peculiarities, is unique not only in Armenia but also in the whole Caucasus ecoregion.

Since 2002, administrative, scientific, practical and organizational activities in the reserve have been implemented by the Khosrov Forest State Reserve State Non-Commercial Organization (SNCO) of the Bioresources Management Agency under the aegis of the Ministry of Nature Protection of Armenia. According to the reserved charter (RA Governmental decision N 925 from 30 May 2002, Annex 1), the main goals of the reserve establishment are to ensure natural development of water and terrestrial ecosystems of the rivers Azat and Vedi basins, to protect the landscapes and biological diversity including the genetic fund of rare and endangered plants and animals as well as their habitats, to implement scientific research and to create prerequisites for the development of scientific and educational tourism, environmental education and responsibility.

The following protected areas are under the subordination of the Khosrov Forest State Reserve: SNCO:

• Khosrov Forest state reserve, which at present is divided into four districts- Garni (4253ha), Kaqavaberd (4745ha), Khosrov (6860.8ha), and Khachadzor(7354.7ha).
• Goravan Sands state sanctuary (95.99ha)
• Khor Virap State Sanctuary (50.28ha)

Realizing the importance of the reserve, on 26 August 2013 Khosrov Forest State Reserve SNCO was awarded with European Diploma of Protected Areas.

The reserve has wonderful landscapes, rich biological diversity, a huge variety of interesting and important untouched forests that are the result of long-term preservation, proper management plan and structure. The Khosrov Forest is the evidence of the Armenians' caring attitude towards historical monuments. Thanks to their attitude, the virgin forest located near the current capital of Armenia-Yerevan has been preserved for 17 centuries.

The reserve has enjoyed a long-term reputation of a forest tract with spectacular scenery and a rich historical legacy which is the closest piece of pristine nature to the capital agglomeration. Wildlife conservation and nature protection began in Armenia many centuries ago.

The reserve was founded by King Khosrov III of the Kingdom of Armenia who ruled from 330 until 339, whom the reserve is named after. Khosrov ordered the forest to be a reserve to improve the natural-climatic conditions of the adjacent city of Artashat to ensure conservation and enrichment of flora and fauna. He also ordered plantation of trees on the high slope of the mountains. It also served as a royal ground for hunting, to complete military exercises and entertainment. Later the forest was enriched with hunting animals brought in from other places, especially from Iran. This reserve that Khosrov had founded was the only state forest reserve in the Roman Empire and among the first in that region. Khosrov was the first Christian monarch as a ruler of state to establish a conservation reserve and was the only known monarch as a descendant of the Diadochi, and a distant relation of Greek King Alexander the Great and as a distant paternal relation of the Persian King Darius I to do so.

According to Faustus of Byzantium, there were two fenced forests one called 'Tachar Mayri' (Sacred Forest) and 'Khosrovakert', which both of them were established on both banks of the Azat River. The Tachar Mayri forest started from the Garni Temple and stretched to the city of Dvin. Khosrovakert was established between Artashat and Dvin along the reeds. Over centuries the Khosrovakert disappeared and the remaining Tachar Mayri was later merger with the natural forest. Another Armenian historian Moses of Chorene, mentions in his writings the history of the forest. According to Moses of Chorene, the expression 'Khosrov Forest' is associated with King Khosrov. Also people in Armenia perpetuate the name of King Khosrov not only to the name of the forest but to settlement, river and mountain (Khosrovasar Mountain) of the monarch's name. The Silk Road had passed through the territory of the reserve.

In the era of the Soviet Union the Khosrov Forest was set aside as forestry and on 13 September 1958 the Garni Forestry was granted a status of Khosrov (then Garni) Reserve. The size of the reserve then was 148.61km2. The reserve became a protected area because the high-quality freshwater supplies the Azat River which flows down to Yerevan and the surrendering forests. In 1990 the reserve became 291.96km2 which some adjacent lands were incorporated in it and in 2006–2007, the reserve was reduced to 238.78km2.

The reserve has been official status to the IUCN Ia category. Since 1995, the reserve has been subordinated to the Ministry of Nature of Protection of Armenia, managed through its Agency for Biological Resources Management and operating as the Khosrov Reserve non-profit organisation. Between 2006 and 2007, a process was underway to develop and approve a management plan for the reserve which aims to improve the reserve's environmental and socio-economic status which came from a 1993 compliance from the Convention on Biological Diversity.

In the first quarter of 2008, rural schoolchildren in the largest villages adjoining the reserve were involved in an awareness-raising program about the reserve. Among the programs was the campaign on leopard conservation as the reserve is one of the 'hotpots' for the Persian leopard. On 9 September 2008 the Visitor Center in the Garni district of the reserve was opened for the visiting public and tourists to educate visitors and bring awareness about the reserve on its natural and human history. On 4 April 2012 the reserve was awarded with a European environmental and conservation diploma from the Council of Europe.