Esteban José Martínez Fernández y Martínez de la Sierra, or simply Esteban José Martínez (1742–1798) was a Spanish navigator and explorer, native of Seville. He was a key figure in the Spanish exploration of the Pacific Northwest.
In 1755 or 1756 Martínez joined the marine Colegio de San Telmo in Seville, a school for pilotos (a non-commissioned naval rank equivalent to Master). By 1773 he was a piloto segundo (second class piloto) at the Naval Department of San Blas in the Viceroyalty of New Spain (present day Mexico).
The Spanish had explored and claimed the Pacific Northwest region in 1774 under Juan Pérez, and in 1775 under Bruno de Heceta and Juan Francisco de la Bodega y Quadra. In the 1774 Pérez expedition Martínez was second in command of the frigate Santiago. The expedition had the first recorded European contact with the indigenous Haida people of the Queen Charlotte Islands in July 1774. The Russian America colonization in Alaska was a threat to Spanish territory claimed there and in the upper Pacific Northwest.
In 1789 the Viceroy of New Spain, Manuel Antonio Flores, instructed Martínez to occupy Nootka Sound, on Vancouver Island in present day British Columbia, build a settlement and fort, and to make it clear that Spain was setting up a formal establishment. The Russians were threatening to take the sound, and in May 1788 the British fur trader John Meares had used Nootka Sound as a base of operations and claimed purchase of land there from the indigenous Nuu-chah-nulth people. Martínez, then ranked piloto primero and alférez de navío (Ensign or Sub-Lieutenant), lead an expedition that arrived at Nootka Sound in early 1789. The force consisted of the warship La Princesa, commanded by Martínez, and the supply ship San Carlos, under Gonzalo López de Haro. He gave Nootka Sound the name Puerto de San Lorenzo de Nuca. The expedition built a settlement there named Santa Cruz de Nuca, including houses, a hospital, and the presidio Fort San Miguel.