Ninju (仁寿) was a Japanese era name (年号,, nengō,; lit. "year name") after Kashō and before Saikō. This period started in April 851 and ended in November 854. During this time, the emperor was Montoku-tennō (文徳天皇).

| Ninju | 1st | 2nd | 3rd | 4th |
|---|---|---|---|---|
| 851 | 852 | 853 | 854 |
| Preceded by: Kashō |
Era or nengō: Ninju |
Succeeded by: Saikō |