These two countries held a commonwealth from the 16th to 18th century.

Poland and Lithuania held a commonwealth from the 16th to 18th century due to a shared cultural heritage, mutual benefit, and geopolitical considerations. The two countries formed a union, known as the Polish-Lithuanian Commonwealth, in 1569 that allowed them to collectively confront external threats, maintain a balance of power in the region, and strengthen their economies. Additionally, their alliance was driven by a sense of shared history, language, and religion, which further solidified their commonwealth and led to a period of significant political, economic, and cultural growth.