A packer is someone or something that packs items into containers, boxes, or bags. In a warehouse, packers carefully arrange products into shipping boxes, making sure fragile items are cushioned and everything fits securely. At a grocery store, the person who puts your purchases into bags is a packer.

The word can also refer to a company that processes and packages products. A meat packer is a business that prepares meat from animals and packages it for sale to stores and restaurants. These companies became hugely important in American history: in the late 1800s, Chicago's massive meatpacking plants revolutionized how food reached cities, though the dangerous working conditions there led to important reforms in food safety and workers' rights.

In sports, Packers refers to the Green Bay Packers, a famous NFL football team from Wisconsin. They got their name because they were originally sponsored by a meatpacking company in 1919.

A packer can also be a machine that compresses materials. A trash packer or garbage packer is a truck that squeezes garbage to fit more waste inside, which is why garbage trucks can hold so much more than it seems like they should.