A magnetic stirrer, or magnetic mixer, is a laboratory device that uses a rotating magnetic field to spin a stir bar immersed in liquid, allowing the sample to mix quickly and evenly. Because the magnetic field passes through glass effectively, it works especially well with beakers and laboratory flasks used in chemistry and biology.

Magnetic stirrers are often preferred over gear-driven motorized stirrers because they are quieter, more efficient, and have no moving external parts to break or wear out. They are also easier to clean and sterilize, do not require lubricants that could contaminate the vessel, and can be used in closed systems without complicated rotary seals. The HP9 model also includes a heated plate for applications that require controlled heating during stirring.