Introduction:
Mahajanapadas were the sixteen powerful kingdoms that existed in ancient India from the 6th to 4th century BCE. Republics, on the other hand, were a form of government where the power was held by the people and their elected representatives. In ancient India, there were several republics that coexisted with the Mahajanapadas.

Mahajanapadas:
The 16 Mahajanapadas were:

1. Anga
2. Magadha
3. Vajji
4. Malla
5. Chedi
6. Vatsa
7. Kuru
8. Panchala
9. Matsya
10. Surasena
11. Assaka
12. Avanti
13. Gandhara
14. Kamboja
15. Kashi
16. Kosala

Republics:
The republics that existed in ancient India were:

1. Vaishali: Located in modern-day Bihar, it was one of the most powerful republics of ancient India.
2. Mallas: They were a confederation of republics located in modern-day Uttar Pradesh and Bihar.
3. Koliyas: They were located in modern-day Uttar Pradesh and were known for their democracy and egalitarianism.
4. Shakya: This republic was located in modern-day Nepal and was known for its democratic traditions.
5. Lichchhavis: They were located in modern-day Nepal and were known for their democratic and republican traditions.

Comparison:
The Mahajanapadas were powerful kingdoms ruled by a king or a monarch, whereas the republics were governed by elected representatives. The Mahajanapadas were often engaged in wars and conflicts with each other, while the republics maintained a peaceful coexistence. The Mahajanapadas had a hierarchical social structure, while the republics were more egalitarian in nature.

Conclusion:
In conclusion, the Mahajanapadas and republics were two distinct forms of governance that coexisted in ancient India. While the Mahajanapadas were powerful kingdoms ruled by a king or a monarch, the republics were governed by elected representatives and were more democratic in nature.