The government of the roman chatholic church however ( ie the vatican) is arguably (for some refuse to accept its status as a nation in and of itself) the only other canidate for the position of worlds oldest and predates everyone elses governments by a thousand plus years.
True, the Church has been around for quite some time, but the Vatican, or Vatican City as a government, has only been around since the 1930's, the land being given to the Church for their tacit approval of Mussolini's regime.
"A casual stroll through the lunatic asylum shows that faith does not prove anything." - Friedrich Nietzsche