In season 11, Derek is involved in a fatal car accident while driving to the airport for his final trip to Washington. He is able to hear and process auditory input, but unable to speak. He is recognized by Winnie, one of the victims of a crash he assisted in earlier, who tells the surgeons that their patient's name is Derek and that he is a surgeon as well. The hospital he was taken to was understaffed and his head injury was not detected quickly enough by the interns on duty that night. Although the neurosurgeon on call is paged multiple times, he takes too long to arrive and Derek is declared brain dead. Police arrive at Meredith's door and take her to see Derek, where she consents to removing him from life support. At the time of his death, Meredith was pregnant with their third child. She gives birth to a daughter whom she names Ellis after her mother.

are meredith and derek together when he died?
yes