Belene Island ranks 1st on the list of the most beautiful islands in Bulgaria. The Danube River splits into two streams that travel north and south of the island, forming the island. Belene is part of Bulgarian territory since the international border between Bulgaria and Romania follows the north branch of the river. The island is located in the Danube, north of the town of Belene, and is 14.5 kilometers long and 6 kilometers wide. This island is the fourth largest Danube island, with 41.078 square kilometers at low tide. Parts of the island are submerged during high tide. A pontoon bridge connects the island to the town of Belene.

Belene Island is part of the Belene Islands Complex and the Persina Natural Park, which is home to more than 170 unique aquatic bird species like the glossy ibis, pygmy cormorant, and lesser grey shrike, red-breasted geese, and others. Willows, poplars, and aspens make up the vegetation of Belene Island, which also has some agricultural ground. Alluvial deposits made up the island. Between 1949 and 1953, and 1956 to 1959, the island was home to the Belene concentration camp, which housed political detainees. In the western part of the island, the Belene Prison is still in use as a jail, while the eastern part is a maintained nature reserve.

St. Ivan Island ranks 2nd on the list of the most beautiful islands in Bulgaria. With a surface area of 0.66 square kilometers, St. Ivan Island is the biggest Bulgarian island in the Black Sea. It is located off the Bulgarian Black Sea Coast near Sozopol, a historic town and renowned tourist destination, and is separated from the small neighboring St. Peter Island by a strait several hundred meters long. It is also the tallest of the Bulgarian sea islands, at 33 meters above sea level. It's 920 meters from the Stolets peninsula, where Sozopol's Old Town is a protected natural area.

Apart from its historical significance, the island is also a nature reserve since 1993, with 72 species of birds nesting on the rocks and around the coast, 3 of which are endangered in the world and 15 in Europe. St. Ivan and the adjacent St. Peter Island host Bulgaria's largest colonies of Audouin's gull and Caspian gull. St. Ivan Island is also inhabited by other rare species, such as Mediterranean monk seals. The rocks on the island are covered with black mussels. The island is the only place in Bulgaria where underground rabbits live.

Location: Black Sea, Bulgaria

Area: 0.66 km2

St. Thomas Island ranks 3rd on the list of the most beautiful islands in Bulgaria. The Bulgarian island of St. Thomas (also known as Zmiyski ostrov) is located 15 kilometers south of Sozopol in the Black Sea. It is one of the rare spots in Bulgaria where wild cacti flourish, with an area of 0.012 square kilometers. The Opuntia cactus were transported from the Botanical Garden in Bratislava, Slovakia, and planted under Tsar Boris III's instructions in 1933 by royal botanist Ivan Buresh. Since then, they've engulfed the majority of the island.

St. Thomas Island takes its name from a church dedicated to Saint Thomas that previously stood on the island. The other name, Snake Island, relates to the large number of greywater snakes that live on the island and feed on fish. The island is part of the Ropotamo nature reserve and is located in Arkutino Bay, 0.2 nautical miles southeast of Humata Foreland. In 1955, the first archaeological expedition to the island uncovered the remnants of a modest church and several ancillary structures. Archaeologists discovered an ancient Thracian settlement from the early Iron Age, ancient Thracian ritual pits, a Byzantine settlement from the 5th–6th century AD, a small monastery from the 12th–14th century, and a sunken fortress from Ancient Thrace in the waters during a new archaeological expedition in 2018.

Location: Black Sea, Bulgaria

Area: 83 km2

St. Anastasia Island ranks 4th on the list of the most beautiful islands in Bulgaria. The Bulgarian islet of St. Anastasia is located in the Black Sea. It sits 1.5 kilometers off the shore in Chernomorets, at a height of 12 meters above sea level, and occupies a one-hectare area. It is Bulgaria's sole populated island off the Black Sea coast. Electricity and drinking water are available on the island. It has the name of the old St. Anastasia convent that formerly stood on the site. The monastery had been in existence since the Middle Ages and was rebuilt in the 18th and 19th centuries. Since 1923, when the island was converted into a prison, it has remained abandoned.

In 1925, Teohar Bakardzhiev led a group of 43 political prisoners (communists and anti-fascists) to revolt and evacuate the island, eventually making their way to the Soviet Union. When the communists took control in 1945, the island was christened Bolshevik Island in their honor. Rangel Valchanov, a Bulgarian film director, based his 1958 film On The Small Island (Bulgarian: "а малки oстров") on this occurrence.

Location: Black Sea, Bulgaria

Area: 0.01 km2

Vardim Island ranks 5th on the list of the most beautiful islands in Bulgaria. The third largest Bulgarian Danubian island is Vardim Island (Bulgarian: остpов ардим, ostrov Vardim) (after Belene Island and Kozloduy Island). It is a protected wetland and bird nesting habitat of national importance located east of the town of Svishtov, near the settlement of Vardim (in Svishtov municipality, Veliko Tarnovo Province) and part of the Belene Danubian Archipelago.

Between the 542nd and 546th kilometers from the Danube's source, the island is roughly 300 meters (980 ft) north of the Bulgarian side. When a section of the island is inundated during the spring high water, an inlet-type forest typically develops. Besides the Vardim oak, a specific hydrophile type of summer oak, other types of oak and elm can be observed on Vardim Island, as well as the white willow, white poplar, black acacia, black poplar, snowflake, etc. According to the Bulgarian Society for the Protection of Birds, the island is one of the five most important nesting areas in the country for the great cormorant, the black-crowned night heron, and the common spoonbill, making it a site of international ornithological importance. A total of 21 nationally protected species are nidificated on the island.

Location: Veliko Tarnovo Province, Bulgaria

Area: 0.987 km2