Sikkim is a landlocked Indian state nestled in the Himalayas. It is the least populous state in India, and the second smallest in area after Goa. Sikkim was an independent state ruled by the Chogyal monarchy until 1975, when a referendum to make it India's twenty-second state succeeded. The thumb-shaped state borders Nepal in the west, the People's Republic of China to the north and east, and Bhutan in the south-east. The Indian state of West Bengal borders Sikkim to its south. The official language is Nepali, and the predominant religions are Hinduism and Vajrayana Buddhism. Gangtok is the capital and largest town.

Despite its tiny size, Sikkim is geographically diverse, owing to its location at the Himalayan foothills. Terrain ranges from tropical in the south to tundra in the north. Kanchenjunga, the world's third highest peak, is located in Sikkim, straddling its northern border with Nepal. Sikkim has become one of India's most visited states owing to its reputation for untouched scenic beauty and political stability.

Sikkim (or Sikhim) means crested land in Nepali. The term, which was coined by the invading Gorkhas, is derived from the Sanskrit word Shikhim which means "crested", and is the most widely accepted origin. Sikkim would thus owe its name to its almost entirely mountainous terrain. An alternative etymology suggests that the name originates in the Limbu words Su, which means "new", and Khyim, which means "palace". Hence the term Sikkim may also mean "New Palace", in reference to the palace built by the state's first ruler, Panchen Namgyal. The Tibetan name for Sikkim is 'Bras mo ljongs, which means the "valley of rice".

The earliest recorded event related to Sikkim is the passage of the Buddhist saint Guru Rinpoche through the land in the 8th century. The Guru is reported to have blessed the land, introduced Buddhism to Sikkim, and foretold the era of monarchy in the state that would arrive centuries later. In the 14th century, according to legend, Khye Bumsa, a prince from the Minyak House in Kham in Eastern Tibet, had a divine revelation one night instructing him to travel south to seek his fortunes. His descendants were later to form the royal family of Sikkim. In 1642, the fifth generation descendant of Khye Bumsa, Phuntsog Namgyal, was consecrated as the first Chogyal (king) of Sikkim by the three venerated Lamas who came from the north, west and south to Yuksom, marking the beginning of the monarchy.

The thumb-shaped state of Sikkim is characterised by wholly mountainous terrain. Almost the entire state is hilly, with the elevation ranging from 280 metres (920 feet) to 8,585 metres (28,000 feet). The summit of the Kanchenjunga is the highest point. For the most part, the land is unfit for agriculture because of the precipitous and rocky slopes. However, certain hill slopes have been converted into farm lands using terrace farming techniques and is used for cultivation. Numerous snow-fed streams in Sikkim have carved out river valleys in the west and south of the state. These streams combine into the Teesta and its tributary, the Rangeet. The Teesta, described as the "lifeline of Sikkim", flows through the state from north to south. About a third of the land is heavily forested.

The lofty Himalayan ranges surround the northern, eastern and western borders of Sikkim in a crescent. The populated areas lie in the southern reaches of the state, in the Lower Himalayas. The state has twenty-eight mountain peaks, twenty-one glaciers, 227 high altitude lakes, including the Tsongmo Lake, Gurudongmar and Khecheopalri Lakes, five hot springs, and over 100 rivers and streams. Eight mountain passes connect the state to Tibet, Bhutan and Nepal.