Lars Magnussen Slagsvold (24 April 1887 – 2 September 1959) was a Norwegian veterinarian.
He was born in Romedal as a son of farmer Magnus Slagsvold (1854–1921) and Inger Krogstie (1855–1924).
After several years of practice he was hired as a head of department in the National Veterinary Institute in 1924.
He was a professor at the Norwegian School of Veterinary Science from 1936 to 1946, and from 1946 to 1957 he headed the State Animal Authority.
[2] Slagsvold was also noted for his work to eliminate the diseases bovine tuberculosis and brucellosis, together with Niels Thorshaug and Halfdan Holth.