Does Judiasm require one to believe that there will be an actual person who will be the Messiah or is belief in a Messianic period (brought about by God) enough for one to believe in?
See Who is Moshiach Ben Joseph and what does/did he do? for a discussion for what Mashiach the person may accomplish during his lifetime.
The gemara Succah (52b) discusses a person known as 'Mashiach ben Yosef' who is destined to die during Gog U'Magog. Moreover, the Rambam Melachim (11:1) describes how the King Mashiach will develop a monarchy. It's a stretch to understand Mashiach referring to anything but an individual person based on these sources.