Mangrove Partners Master Fund

Mangrove Partners Master Fund, Ltd. is one of the flagship funds of Mangrove Partners, a Greenwich, Connecticut-based investment management firm founded in 2010 by Nathaniel August. Mangrove Partners operates as a private hedge fund manager, employing an opportunistic, value-oriented investment strategy. As of late 2025, the firm managed approximately $2.7 billion in discretionary assets for sophisticated individual and institutional investors. Mangrove Partners is a private, independent firm.

Mangrove Partners is not an operating company and has no products or services outside of investment management. The firm's strategy focuses on what it considers inefficient markets and underfollowed investments, including long/short equity positions, distressed debt, and various arbitrage opportunities. The firm takes both long and short positions, aiming to profit from what it identifies as undervalued securities or companies with flawed business models. It is known as an activist investor and is included in the SharkWatch50 list of prominent activist investors.

The firm's patent-litigation posture is that of a financial activist, not a patent-assertion entity (NPE). The database shows one case as a plaintiff and none as a defendant, which reflects the firm's petition to challenge the validity of another company's patents. This action is consistent with an activist investment strategy, where invalidating key assets of a publicly traded company could be financially advantageous, for example, to a short-seller. Mangrove is not asserting patents of its own.

The single tracked case is Mangrove's successful challenge of patents held by VirnetX Inc., a well-known patent assertion entity. In 2015, Mangrove Partners Master Fund filed a petition for inter partes review (IPR) at the Patent Trial and Appeal Board (PTAB) against a VirnetX patent, and was later joined by Apple Inc. The PTAB ultimately found the challenged patent claims unpatentable, a decision that was largely affirmed by the U.S. Court of Appeals for the Federal Circuit after a remand. This use of the PTAB system by a hedge fund to challenge patent validity represents a notable form of financial activism.