膨压（英语：turgor pressure）是指当水进入植物细胞后，使细胞产生向外施加在细胞壁上的压力。

• 提供植物细胞的支持力，使它能维持形状。
  • 草本植物由于缺少木本植物所拥有的坚硬木质素，故其支持力依赖膨压。

Turgor pressure pushes the plasma membrane against the cell wall of plant, bacteria, and fungi cells as well as those protist cells which have cell walls.

This pressure, turgidity or turgidness, is caused by the osmotic flow of water from an area of low solute concentration outside the cell into the cell's vacuole, which has a higher solute concentration. Healthy plant cells are turgid and plants rely on turgidity to maintain rigidity. In contrast, this phenomenon is not observed in animal cells which have no cell walls to prevent them from being burst by the flow of water into the cell and must either continually pump out water, with a contractile vacuole, or live in an isotonic solution where there is no osmotic pressure.