Post-baccalaureate students who wish to study at Harvard, but are not enrolled in the Graduate School, may apply for Special Student status. For more information, see "Special Students" under Non-Degree Programs at the Graduate School of Arts and Sciences.
Individuals holding a doctoral degree (or equivalent academic or professional experience), as well as ABD doctoral candidates, may apply for Visiting Fellow status to pursue independent research at Harvard. Please see "Visiting Fellows" under Non-Degree Programs in the Graduate School of Arts and Sciences.
The Harvard Extension School offers open-enrollment courses (credit or noncredit) in the evening and online, including classes in Latin, ancient Greek, and classical literature and culture (current course listings). Classics courses may also be counted toward degree programs in the Extension School.
EdX offers free online courses from various universities. Among the Classics offerings is "The Ancient Greek Hero in 24 Hours," led by Professor Gregory Nagy, which may be audited or taken for credit through the Harvard Extension School.