Let be a locally convex topological vector space and let be a compact subset of . In functional analysis, Milman's theorem is a result which says that if the closed convex hull of is also compact, then contains all the extreme points of .
The importance of Milman's theorem is subtle but enormous. One well-known fact from functional analysis is that where denotes the set of extreme points of . Ostensibly, however, one may have that has extreme points which are not in . This behavior is considered a pathology, and Milman's theorem states that this pathology cannot exist whenever is compact (e.g., when is a subset of a Fréchet space ).
Milman's theorem should not be confused with the Krein-Milman theorem which says that every nonempty compact convex set in necessarily satisfies the identity .