Commodore João Paulo Ramalho Marreiros was born in Lisboa, in 1966. He joined the Navy in 1984 and graduated from the Escola Naval in 1989. He attended the Junior Officer Course at the Naval War College Course in 1998/99 and the General Officer Course at the Military University Institute in 2016/17, both in Lisboa. He holds a Master of Engineering in Geodesy and Geomatics at the University of New Brunswick, Canada, in 1997, and a Phd in Surveing Engineering at University of Porto, Portugal, in 2013.
After graduation, as junior officer, he served on the frigate N.R.P. “Captain Sacadura Cabral” in 1989/91. He specialized in Hydrography in 1991/92 and was sencond-in-charge of the Hydrographic Brigade until 1994. In 1994/95 he served on board the Hydrographic Ship N.R.P. “Almeida Carvalho” and in  the Hydrography Division of the Hydrographic Institute, 1997/98.

In October 1999, after being promoted Lieutenant Commander, he became Officer in Charge of the 2nd Hydrographic Brigate for two years. In 2001 he was the Officer in Charge for the Hydrographic Equipments, Systems and Methods Department at Hydrographic Division of the Navy Hydrographic Institute for one year. During this period, he was also instructor of the Specialization Course in Hydrography.

In January 2003 he was appointed Commander of the Hydrographic Ship N.R.P. “D. Carlos I” for almost three years. In November 2005, he returned to the Navy Hydrographic Institute as an assistant of the Technical Director and in January 2006 he was appointed commander of the Hydrographic Ships Group, until July 2009, when he was appointed as Director of the School of Hydrography, until July 2013.

Currently, he teaches Hydrography at Escola Naval, since November 2013, and he was the Escola Naval Academic Dean since September 2014 until October 2017. Since October 2018 he served at the Military University Institute as coordinator of the Military Behaviour, Leadership, Logistics, Economics and Management education department, until September 2019. Since July 2019 he is in charge of the Research and Development Centre and Scientific Coordinator of the Master in Military Sciences.
Captain Ramalho Marreiros has published technical articles in the subject of hydrography, geodesy and military sciences.  He has received several commendations and has been awarded with one Exemplar Behaviour Medal (gold), one Naval Cross (1st class) one Military Merit Medal (2nd class) and four Distinguished Services Medals (silver).