RV Marcus Langseth is a research vessel operated by the Lamont–Doherty Earth Observatory (LDEO) of Columbia University as a part of the University-National Oceanographic Laboratory System (UNOLS) fleet.

[1][2] The Marcus G. Langseth was dedicated on December 4, 2007, came into service in early 2008, replacing the RV Maurice Ewing.

[3] Marcus G. Langseth is intended primarily to collect multichannel seismic data, including 3-D surveys.

[citation needed] In March 2009 Chinese authorities denied the vessel permission to pass between Taiwan and China.

[4] In August 2009, Marcus G. Langseth was named in a Canadian lawsuit seeking to halt its seismic tomography experiment.