An agreement between a company or the underwriters on the one hand, and a stockholder on the other hand, that is executed during a registered securities offering. In the lock-up agreement, the stockholder agrees that it will not sell its shares of the company for a specified period of time after the effective date of the registration statement or after the date of the underwriting agreement. The typical lock-up period in an initial public offering is for 180 days; in a follow-on offering, the lock-up period is usually 90 days. See also overhang analysis.

For more information on lock-up agreements, see Practice Note, Underwriting Agreement Commentary: Covenants.