Hello! Can I apply for an EB3, unskilled, visa if I have a PhD? Or will I be over-qualified?

Yes, you can, but a question at interview may be whether you actually have an intention to stay in the job “permanently” on a full-time basis. Although US immigration law does not bind an individual to a sponsored green card job permanently (US law does not allow servitude), immigration and consular officers are authorized to determine whether applicants have an intent to take the offered job on a long-term basis. Possessing a PhD education may raise the question. Due to the limitations of the Lawyers.com Forums, Alan Lee & Arthur Lee, Esqs.’ (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.