Rila Monastery Nature Park (Bulgarian: Природен парк „Рилски манастир“) is one of the largest nature parks in Bulgaria, spanning a territory of 252.535 km2 (97.504 sq mi) in the western part of the Rila mountain range at an altitude between 750 and 2,713 metres (2,461 and 8,901 ft).

It is in Rila Municipality, Kyustendil Province and includes forests, mountain meadows, alpine areas, and 28 glacial lakes.

The park includes one nature reserve, Rila Monastery Forest, with an area of 36.65 km2 (14.15 sq mi), or 14% of its total territory.

The endemic Rila oak (Quercus protoroburoides) inhabits only the Rilska River valley within the park's boundaries and is of special conservation significance.

Its territory is included in the European Union network of nature protection areas Natura 2000 under the code Rila Monastery BG0000496.

The Bulgarian emperors Ivan Asen II (r. 1218–1241) and Kaliman I (r. 1241–1246) donated to the monastery lands, forests and pastures in the valley of the river Rilska, as well as in the regions of Kyustendil, Blagoevgrad, Melnik and Razlog.

[6] Emperor Ivan Shishman (r. 1371–1395) reconfirmed the monastery's privileges and further increased its territory with the Rila Charter which describes the borders of the lands.

It is entirely located in Rila Municipality of Kyustendil Province with coordinates between 42°03' and 42°11' northern latitude and 23°12' до 23°32' eastern longitude.

The park encompasses the western part of the mountain within the catchment area of the rivers Rilska and Iliytsa.

[11] The zones of the Rila mountain range that fall within the park are formed mainly by metamorphic rocks – gneiss, biotite gneiss, amphibolite, mica, schist and marble, bordering to the north and to the east with coarse-grained granite, granite-gneiss, smooth-grained granite and pegmatite veins.

During the glacial periods the limits of the permanent snow cover were at 2200 m. The glaciers melted down 10–12000 years ago.

They were of Alpine type and descended into the valleys reaching as low as 1200–1300 m. Evidence of that limit are the moraines along the river Rilska at 1250 m altitude.

The rugged terrain and the thermocline of 0.7 °C per 100 m determine the significant climate difference between the regions with lower and higher altitude in the park.

Above these ecosystems are located xerothermic oak forests, dominated by sessile oak (Quercus petraea), whose upper zones are covered by European beech, European silver fir (Abies alba) and Bulgarian fir (Abies borisii-regis).

[23] Secondary ecosystems that replace primeval forests cover 5% of the park consist mainly of common aspen (Populus tremula), silver birch (Betula pendula) and common hazel (Corylus avellana) replacing spruce and pine forests.

[24] Alpine ecosystems cover 20% of the park's area at 2200–2500 m and are dominated by dwarf mountain pine (Pinus mugo).

Other species in these ecosystems are green alder (Alnus viridis), Waldstein's willow (Salix waldsteiniana), common juniper (Juniperus communis), Chamaecytisus absinthioides and Festuca valida.

The highest concentration of species is found in the Rila Monastery Forest Reserve, the valleys of the rivers Iliyna and Radovichka, and at the foothills of Kalin peak.

[29] Balkan endemic species include Bulgarian avens (Geum bulgaricum), yellow mountain lily (Lilium jankae), Fritillaria gussichiae, etc.

The highest moss concentrations are found in and along the rivers Rilska and Iliyna, their tributaries and the wet meadows in the Alpine zone.

[36] The species distribution by forest ecosystems is as follows: beech (69), alder (47), spruce and fir (80), and Macedonian pine (36).

[42] Rila Monastery Nature Park is an important sanctuary of the hazel grouse, rock partridge, western capercaillie, Eurasian pygmy owl, boreal owl, black woodpecker, white-backed woodpecker, red-breasted flycatcher, wallcreeper, Alpine accentor and Alpine chough.

[42] There are 12 reptile species, not counting the spur-thighed tortoise which breeds just outside the park's limits near the village of Pastra.

[44] Of national importance are the populations of the slowworm, viviparous lizard, smooth snake and common European viper.

[46] Some of the endangered species include beetles: Calosoma sycophanta, Carabus intricatus, Morimus funereus; net-winged insects: Libelloides macaronius; ants: Formica lugubris, Formica pratensis, Formica rufa; butterflies: Parnassius apollo, Parnassius mnemosyne, Euphydryas aurinia, Polyommatus eroides, Apatura iris, Carterocephalus palaemon, Colias caucasica, Erebia rhodopensis, Charissa obscurata, Limenitis populi, Melitaea trivia, Zerynthia polyxena, etc.

[47] The principal architectural monument in the park is Rila Monastery, situated at an altitude of 1147 m and declared a UNESCO's world heritage site in 1983.

[49] The monastery was founded by the medieval Bulgarian hermit and saint John of Rila during the reign of emperor Peter I of Bulgaria (r.

In the 13th century the relics of John of Rila were transferred to the capital Tarnovo but after the fall of the Bulgarian Empire under Ottoman rule they were returned to the monastery in 1469.

[49][50] The monastery complex covers an area of 8,800 m2 and consists of a church, a defensive tower and monastic apartments encircling an inner yard.

The five-storey tower contains a chapel dedicated to the Transfiguration and decorated frescoes dated from the second half of the 14th century.