Officially, it is 5'9, as it also is in the USA. In Germany, the average man stands at around 5'8, while in France, it is little more than 5'7. The tallest people in the world are the Dutch, with the men averaging around 6'.
A point to note is the fact that the average figures take into account ALL men. Hence, a young man may feel tall compared to the average, as a result of not taking note of the fact that, in relative terms, he is not so tall. For example: at six-foot-tall, I could easily consider myself to be three inches above the average height for a man (which I am), but would not be taking into account the fact that, for my age, it is not so tall. At six foot, I can honestly say that I feel little more than average height, as I'll frequently have a group of guys all taller than me pass me (and I'm not talking here about a Basketball team). I've heard, and I'd say, that, for the 18-25 category of men, 5'11 was average. I think that, as said, one feels more small when stood next to a taller guy, than they do small when stood next to a shorter guy. If standing next to my 5'4 mate, I feel less tall than I would small stood next to a 6'8 guy. This said, we take relative notice of taller people, and feel relatively different in size to whom (i.e. as compared with how we do different in size when stood next to smaller people).
People DO tend to exaggerate their heights. For example, a person of my acquaintance who is a good half an inch shorter than myself, claims to be 6'2. I resist the temptation to correct him. 6' used to be a great height (my grandparents and even my parents consider me to be very tall, while I'm more the high side of average), but is not so anymore.