The 21-year-old was found with knife wounds near the viewing point at the north London beauty spot on Tuesday.
The Metropolitan Police said Ogunyankinnu, 27, of Southbury Road in Enfield, was arrested on Friday, April 10.
He was charged with m8rder on Sunday, April 12.
Ogunyankinnu is due to appear at Stratford Magistrates’ Court on Monday.
A 25-year-old man who had been arrested on suspicion of assisting an offender has been released with no further action.
The Met said the investigation was still ongoing.
Sullivan was a film student at the London Screen Academy. His father, Chris Sullivan, 65, told BBC London he had lost his only son, who was referred to by friends and family as Fin.”
“All of his friends said he was the light, the leader. His friends’ parents loved him. This is why it’s so tragic,” he said.
Another man, aged in his 20s, was also discovered with st@b injuries by officers on nearby Regent’s Park Road on Tuesday.
He was taken to hospital, where his injuries were assessed as not life-threatening or life-changing.
