Santa Cruz (, officially the Municipality of Santa Cruz (; ), is a municipality in the province of Ilocos Sur, Philippines. According to the , it has a population of people.
The place now known as Santa Cruz was the site where Captain Juan de Salcedo landed to get provisions, especially water, on his way to pacify the north. As soon as they came ashore, his men immediately went to the top of the highest sand dune and planted a big wooden cross to signify that the place has been conquered (like what they did later in Santa Catalina). This cross is visible to mariners passing by, often describing the place as "Santa Cruz." The cross may have vanished, but the name Santa Cruz stuck, especially with natives who became Christians.
The Municipality of Santa Cruz is bordered by the municipalities of Santa Lucia and Salcedo to the north, Sigay and Suyo to the east, and Tagudin to the south
Santa Cruz is situated from the provincial capital Vigan, and from the country's capital city of Manila.
Santa Cruz is politically subdivided into 49 barangays. Each barangay consists of puroks and some have sitios.
In the 2024 census, Santa Cruz had a population of 41,296 people. The population density was .
The predominant dialect spoken in Santa Cruz is Ilocano.
Santa Cruz, belonging to the second congressional district of the province of Ilocos Sur, is governed by a mayor designated as its local chief executive and by a municipal council as its legislative body in accordance with the Local Government Code. The mayor, vice mayor, and the councilors are elected directly by the people through an election which is being held every three years.
The Sta. Cruz Schools District Office governs all educational institutions situated within the municipality.