| Conflict: | Siege of Nagakubo |
| Partof: | the Sengoku period |
| Date: | 1543 |
| Place: | Nagakubo, Shinano Province |
| Result: | Takeda victory |
| Combatant1: | Forces of Oi Sadataka |
| Combatant2: | Takeda clan |
| Commander1: | Oi Sadataka |
| Commander2: | Takeda Shingen |
| Strength1: | 1,200 |
| Strength2: | 3,000 |
The siege of Nagakubo (長窪城) was a battle of Japan's Sengoku period. It took place in 1543 as part of Takeda Shingen's bid to control Shinano Province, Japan. He took the castle of his former ally, Oi Sadataka, who had deserted him to ally with Murakami Yoshikiyo. Oi was sent to Takeda's home city of Kōfu as a prisoner, where he was then killed.