ISO 3103 is a standard published by the International Organization for Standardization (commonly referred to as ISO), specifying a standardized method for brewing tea, possibly sampled by the standardized methods described in ISO 1839. It was originally laid down in 1980 as BS 6008:1980 by the British Standards Institute. It was produced by ISO Technical Committee 34 (Food products), Sub-Committee 8 (Tea).

The abstract states the following:

The method consists in extracting of soluble substances in dried tea leaf, containing in a porcelain or earthenware pot, by means of freshly boiling water, pouring of the liquor into a white porcelain or earthenware bowl, examination of the organoleptic properties of the infused leaf, and of the liquor with or without milk, or both.

This standard is not meant to define the proper method for brewing tea, but rather how to document tea brewing procedure so sensory comparisons can be made. An example of such test is a taste-test to establish which blend of teas to choose for a particular brand in order to maintain a consistent tasting brewed drink from harvest to harvest.