Introduction:
The river that enters Orissa from West Bengal is the Subarnarekha River.

Explanation:
The Subarnarekha River is one of the major rivers in the Indian states of West Bengal and Orissa. It originates in the Chota Nagpur plateau in Jharkhand and flows through West Bengal before entering Orissa.

Key Points:
- The Subarnarekha River is approximately 395 kilometers long.
- It originates from the Ranchi district of Jharkhand and flows through the districts of Purulia and West Midnapore in West Bengal.
- After crossing the border of West Bengal and Orissa, the river flows through the districts of Mayurbhanj and Balasore in Orissa.
- The river finally merges with the Bay of Bengal near the Chandipur beach in Orissa.
- The Subarnarekha River is known for its rich mineral deposits, including gold (subarn means gold, and rekha means line).
- The river basin is also rich in other minerals like iron ore, copper, and manganese.
- The river is an important source of water for irrigation, as well as for industrial and domestic purposes in the region.
- The Subarnarekha River is also significant in terms of biodiversity. It supports a variety of flora and fauna, including several species of fish and birds.
- The river and its surrounding areas are also known for their scenic beauty, attracting tourists and nature enthusiasts.

Conclusion:
The Subarnarekha River enters Orissa from West Bengal. It is a major river in the region, known for its mineral deposits, biodiversity, and scenic beauty.