In something approaching exasperated frustration, Metal Gear creator Hideo Kojima has revealed via Twitter that the upcoming Ground Zeroes is not, in fact, Project Ogre.

After voicing his satisfaction at Ground Zeroes' warm reception during PAX, he went on to complain that "I'm sick & tired of people keep asking me like "is that project Ogre?" here in Seattle everyday. Project Ogre is what the project that Ogre appears. Ogre does not appear in "MGS Ground Zeroes" trailer".

It isn't yet clear what Project Ogre actually is, though a degree of confusion is certainly understandable. Both projects run on the impressive Fox Engine, for example, and in a CNN interview last year Kojima mentioned that Ogre would feature an open world - much like Ground Zeroes has been revealed to include.
"The kind of game I'm making is some game that has a very wide entrance, a very open entrance," Kojima told the network. He also noted that instead of crafting an overly cinematic experience, he wanted to "make something very free".
The article in question also revealed how Kojima had told them how "players should still be able to find new sights and worthwhile adventures after having played the game for as many as 100 hours", moreover.

Beyond these year old details, it's difficult to tell what Project Ogre could be. Previously 'leaked' screenshots displaying the title 'Metal Gear Solid 5' with 'Open Ground Reconnaissance Endeavour' emblazoned above (which, taken together, form the acronym OGRE) hinted at the title's possible identity, but if Konami's UK Twitter account is anything to go by these rumours are likely to be fake.