Mortimer is an English lord who has been imprisoned for most of his life.
Richard II’s chosen heir, he was displaced by King Henry’s grandfather, Henry IV, when the latter usurped the throne. He was part of a rebellion against the latter which failed, after which he was sent to jail (see Henry IV, Part One). Knowing himself to be dying, he calls his nephew Richard Plantagenet to his side to tell him of all this and let the young man know that he has more right to the throne than does the current King. He is very old, weak, and almost blind. Historically he is the same as the Mortimer of Henry IV, Part One.