The State of Sikkim is surrounded by

The state of Sikkim is a landlocked region in the eastern Himalayas with significant strategic importance due to its international and domestic borders. It is surrounded by three sovereign nations and one Indian state. To the north and northeast, it shares a border with the Tibet Autonomous Region of China [3]. To the west, it is bordered by Nepal [1]. To the southeast, it shares a boundary with Bhutan. Domestically, Sikkim is bordered to the south solely by the Indian state of West Bengal [2]. While other northeastern states like Assam are nearby, they do not share a direct land border with Sikkim, as the state is separated from the rest of India by the Siliguri Corridor and West Bengal's northern districts. Therefore, the surrounding entities are China, Nepal, Bhutan, and West Bengal.

Sources

1. [3] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 16: India–Political Aspects > The Sino-Indian Border Dispute > p. 29
2. [1] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 16: India–Political Aspects > India-Nepal Boundary > p. 46
3. [2] Modern India ,Bipin Chandra, History class XII (NCERT 1982 ed.)[Old NCERT] > Chapter 10: India And Her Neighbours > Relations with Sikkim > p. 179