25 major rivers in Bihar, India:
1. **Ganges (Ganga)**
   - **Origin:** Gangotri Glacier, Uttarakhand
   - **Length:** 2,525 km
   - **Description:** The Ganges is the most significant river in Bihar, providing water for irrigation, transportation, and being a vital cultural and religious symbol. Major cities like Patna and Bhagalpur are situated on its banks.

2. **Kosi**
   - **Origin:** Himalayas, Nepal
   - **Length:** 720 km
   - **Description:** Known as the "Sorrow of Bihar" due to frequent floods, the Kosi river basin is critical for agriculture in the region.

3. **Gandak**
   - **Origin:** Nepal
   - **Length:** 630 km
   - **Description:** The Gandak river serves as a key source for irrigation and hydropower in northern Bihar. It also forms the Gandak River Barrage.

4. **Son**
   - **Origin:** Amarkantak, Madhya Pradesh
   - **Length:** 784 km
   - **Description:** A major southern tributary of the Ganges, the Son river is crucial for irrigation and sand mining. 

5. **Bagmati**
   - **Origin:** Shivapuri Hills, Nepal
   - **Length:** 589 km
   - **Description:** The Bagmati river plays a key role in irrigation but also faces significant pollution challenges.

6. **Punpun**
   - **Origin:** Chotanagpur Plateau, Jharkhand
   - **Length:** 200 km
   - **Description:** A tributary of the Ganges, the Punpun river provides irrigation and is known for flooding during monsoon season.

7. **Falgu**
   - **Origin:** Gaya, Bihar
   - **Length:** 135 km
   - **Description:** The Falgu river, associated with Hindu religious significance, is primarily a seasonal river known for its use in agriculture.

8. **Kamla**
   - **Origin:** Nepal
   - **Length:** 328 km
   - **Description:** The Kamla river supports irrigation and is prone to seasonal floods.

9. **Balan**
   - **Origin:** Madhubani, Bihar
   - **Length:** 110 km
   - **Description:** The Balan river is a tributary of the Kamla river and aids in local agriculture.

10. **Burhi Gandak**
    - **Origin:** Someshwar Hills, Bihar
    - **Length:** 320 km
    - **Description:** The Burhi Gandak river supports agriculture and drains into the Ganges.

11. **Ghaghara**
    - **Origin:** Tibet
    - **Length:** 1,080 km
    - **Description:** A significant tributary of the Ganges, the Ghaghara river provides water for irrigation and supports a diverse ecosystem.

12. **Mahananda**
    - **Origin:** Himalayas, Darjeeling
    - **Length:** 360 km
    - **Description:** The Mahananda river aids agriculture and has a significant catchment area in Bihar.

13. **Kiul**
    - **Origin:** Jhajha, Bihar
    - **Length:** 110 km
    - **Description:** The Kiul river provides irrigation and merges with the Ganges near Surajgarha.

14. **Harohar**
    - **Origin:** Bihar
    - **Length:** 130 km
    - **Description:** The Harohar river supports agriculture and joins the Kiul river in Lakhisarai.

15. **Chandan**
    - **Origin:** Chandan hills, Bihar
    - **Length:** 82 km
    - **Description:** The Chandan river supports irrigation and merges with the Ganges.

16. **Sakri**
    - **Origin:** Bihar
    - **Length:** 220 km
    - **Description:** The Sakri river supports irrigation and merges with the Kosi river.

17. **Karmanasa**
    - **Origin:** Vindhya Range, Madhya Pradesh
    - **Length:** 192 km
    - **Description:** A tributary of the Ganges, the Karmanasa river is significant for irrigation and boundary demarcation.

18. **Ghugri**
    - **Origin:** Bihar
    - **Length:** 120 km
    - **Description:** The Ghugri river supports local agriculture and joins the Kosi river.

19. **Lalbakeya**
    - **Origin:** Nepal
    - **Length:** 200 km
    - **Description:** The Lalbakeya river is a tributary of the Gandak and supports agriculture in Bihar.

20. **Bhutahi Balan**
    - **Origin:** Nepal
    - **Length:** 320 km
    - **Description:** The Bhutahi Balan river aids in irrigation and is prone to seasonal floods.

21. **Adhwara**
    - **Origin:** Nepal
    - **Length:** 256 km
    - **Description:** The Adhwara group of rivers includes multiple streams supporting agriculture and prone to flooding.

22. **Tiljuga**
    - **Origin:** Nepal
    - **Length:** 206 km
    - **Description:** A tributary of the Kosi river, the Tiljuga supports agriculture and flood management.

23. **Badua**
    - **Origin:** Munger, Bihar
    - **Length:** 67 km
    - **Description:** The Badua river is known for irrigation and minor flood risks.

24. **Karma**
    - **Origin:** Bihar
    - **Length:** 75 km
    - **Description:** The Karma river supports local agriculture and joins the Ganges.

25. **Baya**
    - **Origin:** Gandak Basin, Bihar
    - **Length:** 88 km
    - **Description:** The Baya river aids in irrigation and merges with the Burhi Gandak river.

These rivers collectively form a crucial part of Bihar's ecosystem, providing water for agriculture, supporting livelihoods, and contributing to the state's cultural and religious heritage.