A telethon (a portmanteau of "television" and "marathon") is a televised fundraising event that lasts many hours or even days, the purpose of which is to raise money for a charitable, political or other purportedly worthy cause.

Most telethons feature heavy solicitations for pledges (promises to donate funds at a later time) by masters of ceremonies or hosts, who are often local celebrities or media personalities combined with variety show style entertainment such as singers, bands and instrumentalists. In some cases, telethons feature content related to the cause being supported, such as interviews with charitable beneficiaries, tours of charity-supported projects, or pre-taped sequences. The equivalent term for a radio broadcast is a radiothon; most radiothons do not include live entertainment.

In the United States, the first telethon used for political outreach occurred in 1960.