Cytoplasmic streaming is the movement of cytoplasm within a living cell. Cytoplasmic streaming, also called cyclosis, transports nutrients, enzymes, and larger particles within cells, enhances the exchange of materials between organelles, as well as between cells. In some unicellular organisms, such as amoeba, it provides the mechanism for cell locomotion. It is thought that microfilaments provide the driving force for, and control the direction of, the streaming.

In some plant cells there is a rapid rotatory cytoplasmic movement, limited to the peripheral parts of the cell next to the cell wall, which carries chloroplasts and granules along. This movement may be increased by light, and is dependent on temperature and pH. Auxins, or plant growth hormones, may also increase the rate of movement. In some protozoans, such as the ciliates, slower cyclotic movements transport digestive vacuoles through the cell body.