Castelo Viegas is a former civil parish in the municipality of Coimbra, Portugal. The population in 2011 was 1,695, in an area of 7.11 km. On 28 January 2013 it merged with Santa Clara to form Santa Clara e Castelo Viegas.

The first mention is in 1122 with the name Castel Venegas.

Population of the civil parish of Castelo Viegas (1864–2011) Year Pop. ±% 1864 515 —     1878 586 +13.8% 1890 638 +8.9% 1900 547 −14.3% 1911 531 −2.9% 1920 594 +11.9% 1930 577 −2.9% 1940 657 +13.9% 1950 1,039 +58.1% 1960 1,613 +55.2% 1970 1,096 −32.1% 1981 1,577 +43.9% 1991 1,833 +16.2% 2001 1,771 −3.4% 2011 1,695 −4.3%