Erlenmeyer flasks are conical flasks with wide flat bottoms and tapered necks. The flasks are designed for a variety of laboratory liquid handling applications, including pouring, mixing, storage, and suspension cell culture.

Erlenmeyer flasks are available in a broad range of sizes and come in wide or narrow mouth designs. The tops of the flasks are open and can accommodate a variety of closures, including screw caps and stoppers. Sterile and non-sterile Erlenmeyer flasks are available. Manufactured from numerous materials, the flasks are typically made of glass or plastic. Erlenmeyer flasks can be unmarked or graduated. The volume indicators on graduated Erlenmeyer flasks are approximations and should not be used for accurate measurements.

Erlenmeyer or titration flasks are named after their inventor Emil Erlenmeyer. Their slanted sides and narrow necks allow the contents to be mixed by swirling without the risk of spills, which is useful for titrations and for boiling liquids. The necks can also support filter funnels.

The inside of the mouth of Erlenmeyer flasks may be frosted to accommodate a ground glass stopper. Alternatively, a cap or rubber stopper may be used to contain the contents. Some Erlenmeyer flasks include a side arm (or one can be attached) to enable filtering.

Erlenmeyer flasks can also be used to prepare microbial cultures. Some are fitted with baffles that help maximize gas transfer and further agitate the contents when shaken.