Generations 7 and 8 introduced legendaries that can evolve.
Cosmog evolves into Cosmoem at level 43.
In Sun, Ultra Sun, or Sword, Cosmoem evolves into Solgaleo at level 53.
In Moon, Ultra Moon, or Shield, Cosmoem evolves into Lunala at level 53.
Type: Null evolves into Silvally with high Friendship.
Kubfu evolves into Urshifu Single Strike Style after reading the scroll in the Tower of Darkness.
Kubfu evolves into Urshifu Rapid Strike Style after reading the scroll in the Tower of Waters.