Sancho III of Navarre (c. 985–October 18 1035; nicknamed "The Great"), was Count of Aragon and King of Navarre from 1004 until his death.

Born to García the Tremulous of Pamplona and Jimena Fernández , he ascended the throne in 1004, inheriting Navarre, Aragon, Sobrarbe and Ribagorza. Having gone further than any previous Christian monarchs in uniting the principalities of Spain, his life's work was undone, from a modern point-of-view, when he divided his domains shortly before his death, like any feudal lord, to provide for his sons.

With his nephew, king Alfonso V of Leon and Count García Sánchez of Castile , he led a combined attack against Al-Mansur Ibn Abi Aamir (died 1002; "Almanzor" among the Christians), conquering further territories in the south.

Relation between the three Christian entities soured after the assassination of Count García in 1027. In the ensuing hostilities Sancho occupied first Castile and later on, Leon. This was the height of his rule which extended from the borders of Galicia in the west to the county of Barcelona in the east and he styled himself Rex Hispaniarum, "King of the Spains". Sancho was married to Muña Mayor Sánchez, daughter of count Sancho I of Castile . Besides four legitimate sons he also fathered one by his mistress Sancha de Aybar. Before his death in 1035 Sancho divided his possessions among his sons. Fernando got Castile, García received Navarre and the Basque country and Gonzalo got Sobrarbe y Ribagorza. The illegitimate son Ramiro obtained the county of Aragon, which was elevated to a kingdom.