Mark Joseph Machina (born October 27, 1954) is an American economist noted for work in non-standard decision theory. He is currently a distinguished professor at the University of California, San Diego. The Marschak–Machina triangle, a probability diagram used in expected utility theory, bears his name, along with that of Jacob Marschak.

The Machina Triangle is a way of representing a three dimensional probability vector in a two dimensional space. The probability of a given outcome is denoted by a euclidean distance from the point that represents a lottery (probability).^[1]