The two pizza rule is a guideline for limiting the number of attendees at a meeting.
According to the rule, a meeting should never have so many attendees that they could not all be fed with two pizzas. Generally, this limits the number of attendees at a meeting to less than eight.
The goal of the two pizza rule is to increase productivity and prevent HiPPO and groupthink, phenomena that often occur in large groups which tend to discourage creative thinking. HiPPO, which is an acronym for the "highest paid person's opinion," describes the tendency for lower-paid employees to defer to higher-paid employees. Groupthink occurs when a large group's need for consensus overrides the judgment of individual group members.
The two pizza rule is often credited to Jeff Bezos, founder and CEO of Amazon. Bezos is known to have used two pizza teams to create a decentralized and innovative workplace environment when Amazon was a startup.