Topical or thematic stamp collecting is the practice of collecting postage stamps relating to a particular subject or concept. Topics may include almost anything, from birds on stamps, to famous physicians, to the history of southwest England.

Both collectors of whales and penguins on stamps would want this 1929 issue from the Falkland Islands.

While the earliest stamps simply depicted busts of reigning monarchs, important figures, or coats of arms, the continuing need for new types of stamps, plus the desire to inject some variety, prompted postal administrations to develop new designs that drew upon their nations' cultures, as well as nature. Bears appeared on provisional stamps of St. Louis in 1845, while the beaver was featured on the earlist stamps of Canada. More than 150 years later, the variety of designs on stamps is simply staggering, amounting to at least 100,00 distinct designs, and giving topical collectors plenty to do.

In fact, there are now so many types that traditional topics for collecting, such as "ships" or "birds", have become nearly impossible to complete, and topical collectors may specialize further, such as by looking for only square-rigged sailing ships, or only flightless birds.

Since most types of stamp designs are commonly available and inexpensive, acquiring them is mostly a matter of poring over the stamp catalog looking for relevant types, and learning enough about the topic to recognize subtle connections. The Americal Topical Association and others have published lists of larger topics.

Francis Garnier explored the Mekong River, so this 1943 stamp of French Indochina would likely be part of a topical collection about the river.

Topical collections are a recognized category for competitive exhibition.