Erhard Seminars Training (marketed as est, though often encountered as EST or Est) was an organization, founded by Werner Erhard in 1971, that offered a two-weekend (6-day, 60-hour) course known officially as "The est Standard Training". The seminar aimed to "transform one's ability to experience living so that the situations one had been trying to change or had been putting up with clear up just in the process of life itself". An est website claims that the training "brought to the forefront the ideas of transformation, personal responsibility, accountability, and possibility".

Est seminars operated from late 1971 to late 1984, and spawned a number of books from 1976 to 2011. Est has been featured in a number of films and television shows, including the critically acclaimed spy-series The Americans, broadcast from 2013 to 2018. Est represented an outgrowth of the Human Potential Movement of the 1960s through to the 1970s.

As est grew, so did criticism of it. In 1977, the film Semi-Tough, which parodied the then-popular course, was released. Various critics accused est of mind control or of forming an authoritarian army; some labeled it a cult.

The last est training took place in December 1984 in San Francisco. The seminars gave way to a "gentler" course offered by Werner Erhard and Associates and dubbed "The Forum", which began in January 1985.