A tea infuser is a device in which loose tea leaves are placed for brewing. It performs the same function as a tea bag. The infuser is generally a small mesh or perforated metal container, ranging in size to brew single or multiple servings at once. Common shapes for infusers include spherical (also called a tea ball), conical, and cylindrical. One style of infuser is a split sphere with tong-like handles to open its mesh container.

The infuser is placed in a cup or pot of hot or boiling water, allowing the tea to brew without loose tea leaves spilling into the pot or cup. A rod or chain is commonly attached to the container of the infuser to make retrieval from the pot or cup easier.

When brewing tea using an infuser, it is advisable to fill it only halfway so that the wet leaves can expand and to increase the surface area of the leaves exposed to the boiling water to allow for quicker brewing.