Fanum tax (/fæn.əm.tæks/ ) is an Internet slang term describing the theft of food between friends. Originally coined by American streamer Fanum, the term has become an internet meme, particularly employed and popularized by Generation Alpha.

The first usage of Fanum tax referred exclusively to streamer Fanum, who jokingly "taxed" snacks by taking bites of food from fellow content creators during streams on the broadcasting platform Twitch. In an interview with Wired, Fanum defined the term as:

Let's say your friend having a meal, he's having a good meal, and you just want a piece of that meal. Like, you know what I'm saying? You need a share. That's your friend and the friend's share, right? Get you a little piece of the meal. It's the Fanum tax. You just go ahead and just like, lemme get a little bit of 5%, 10% of the meal, maybe 20%.

The term circulated among the YouTube collective AMP in late 2022 and was popularized especially during Fanum's Twitch streams with popular American YouTuber Kai Cenat, where Fanum would take Cenat’s cookies.

On October 2, 2023, a TikTok account under the username @ovp.9 posted a short video of a character from the online video game Fortnite "singing" to a musical parody of the 2021 song "ecstacy" by Suicidal-Idol. The parody, titled either "Sticking Out Your Gyat for the Rizzler" or "You're so skibidi, you’re so fanum tax", features multiple internet culture terms including gyat, Skibidi Toilet, rizz and Sigma male. The song was used in many videos on TikTok, inspiring the mass creation of videos featuring Minecraft-inspired games on the platform.

The sound was used in over 195,000 videos and amassed over 321 million views on TikTok.

According to Business Insider, many members of Generation Z claim "they were not aware of the meme at all." The New York Times referred to the term as "the language of Gen Alpha."