Project Ogre is Metal Gear Solid 5: The Phantom Pain, Hideo Kojima has confirmed.
Talking to Jeux Video Magazine (translated via Google), Kojima explained that "at the time I could not even talk about the fifth episode Metal Gear, that's why I called [it] 'Project Ogre'.
"This name was chosen to leave clues about what will happen in the game because it is a kind of 'ogres' in the game."
Ogre has long been assumed to be the codename for Kojima's fifth MGS, but this is the first time the director has openly discussed the link.
However, things start to get confusing when you take Kojima's previous comments into account.
Kojima once dismissed Project Ogre as being Metal Gear Solid: Ground Zeroes, but later revealed that Ground Zeroes is a prologue to Metal Gear Solid 5: The Phantom Pain. If Ground Zeroes is a part of Metal Gear Solid 5 but isn't Project Ogre, but Project Ogre is Metal Gear Solid 5, what is Ground Zeroes?
Who knows? It's Friday. It's all Metal Gear. I'm going home.