An initial public offering (IPO) that is conducted by an corporation that was previously a publicly held company and changed its status to a privately held company. The corporation, before going private, carried out an initial public offering, and after going public again is in the process of conducting another offering: it is going public for the second time, with its initial public offering becoming a secondary offering. Such secondary offerings used to grow out of leveraged buyout (LBO) structures (particularly reverse LBOs). Secondary initial public offerings may come in handy for private equity holders who can stage an exit strategy through such offerings, after holding their investments for a while.

It is also known for short as SIPO.