A flyer (also spelled flier or called handbill) is a single page leaflet advertising a nightclub, event, service, or other activity. Flyers are typically used by individuals or businesses to promote their products or services. They are a form of mass marketing or small scale, community communication.

Flyers are typically a 1 page project done at 300dpi for color gloss and 150dpi for black & white. The single "master" is then mass copied via a copy machine.

Flyers are handed out on the street (known as 'flyering'), posted on bulletin boards, or given away at events. Bulletin boards are found on college campuses, in cafes, community meeting houses, laundromats and small markets.

Flyers, along with postcards, leaflets and small posters, are vital and free forms of communication for people who want to engage the public but do not have the money or desire to take out classified advertising in a local newspaper. However, as marketing became more direct in the late 1980s and 1990's, flyers have evolved and currently there are many formats to be found. Some examples are:

 > A4 (letterhead size)
> A5 (half letterhead size)
 > DL (compslip size)
> A6 (postcard size)
> CC (credit card size)

Note: Web Flyers are redone at 72ppi and due to browser scrolling do not have a page size restriction.

Cheap to produce, flyers are usually produced in 300gsm glossy card (whereas a leaflet is produced on a 130gsm/170gsm weight paper) and are a very effective form of direct marketing.

Their widespread use intensified with the spread of desktop publishing systems. In recent years, the production of flyers through traditional printing services has been supplanted by Internet services; customers may send designs and receive final products by mail. Flyers range in tone from humorous to irreverent or absurd.

The Craigslist website is a web-based system that mirrors the sort of community communication that occurs via flyering and bulletin boards.