Lusonectes (meaning "Portuguese swimmer") is an extinct genus of microcleidid plesiosaur from the Early Jurassic (Toarcian) São Gião Formation of Portugal.

The generic name is derived from the prefix Luso, from Latin Lusitania referring to Portugal, and nektes ("swimmer" in Greek).

The holotype, MG33, a partial skull and articulated mandible, was discovered possibly by geologist Paul Choffat and his team during the 19th century within rocks from the São Gião Formation near Murtede, Portugal.

[1] It is based on a single autapomorphy, a broad triangular parasphenoid cultriform process that is as long as the posterior interpterygoid vacuities, and also on a unique character combination.

[1] Smith, Araújo and Mateus (2012) found Lusonectes to belong to the Plesiosauridae[1] when placed within a cladogram created by Ketchum and Benson (2010).