The accident happened on the E16 close to Leirsjøen lake in Lunner, between Grua and Leirsjøen.
The victims were airlifted by helicopter to two separate hospitals following the crash.
Police spokesman Børge Hals told Oppland Arbeiderblad: "Both of the survivors are injured, but, as far as we know, there is no talk of serious injury."
One of the survivors was brought to Ullevål Hospital; the other one to Ahus Hospital. The sheep died immediately.