Some terms that refer to common people en masse include
• hoi polloi, “The common people; the masses”
• masses, with senses such as “People, especially a large number of people”, “The total population”, and “The lower classes or all but the elite”
• plebs, “The common people, as a whole, or as a group”
As these terms refer to bunches of people rather than individuals, they don't quite address the question as asked. However, one can say an individual is “among the hoi polloi”, “from the masses”, “a pleb”, etc.
Edit: Chris Jester-Young comments that “in the same way that Ukraine should not have "the" preceding it, neither should hoi polloi”. I do not care to argue the issue, but will point out two reasons for not agreeing with the comment:
(1) According to Wikipedia's Name of Ukraine article.
Prior to Ukraine's  independence from the USSR, the country was generally called The Ukraine in English, but this usage is on the wane and officially deprecated by the Ukrainian government and many English language media publications.
It is reasonable to avoid the before Ukraine, but the reason for doing so (political correctness) is rather different than avoiding it before hoi polloi (possible redundancy of article).
In short, the “in the same way” portion of the comment is wrong.
(2) It is true that some sources deprecate using the before hoi polloi, but OED says use of a definite article here is normal. Eg, from en.wiktionary Usage_notes:
As hoi represents a definite article in Ancient Greek, some authorities consider that the construction the hoi polloi is redundant and should not be used in English. The OED says "In English use normally preceded by the def. article even though hoi means ‘the’".
In short, whether to avoid the before hoi polloi is not an open-and-shut question, which casts doubt upon the last assertion in the comment.