After the Romans left the island of Britain, the next groups to come to the island were Germanic tribes. These were the groups that have commonly been called Angles, Saxons, and Jutes, though historians now argue that this categorization is too simple as there were other Germanic tribes who came. This happened largely in the 5th and 6th centuries.
It is important to note that this was not an invasion like that of William the Conqueror. Instead, this was more like a gradual infiltration by a number of separate groups. They did not all come as one invading force. Instead, they seem to have come separately, creating a number of different kingdoms in what is now England.