Upsilon (Υ or υ) is the 20th letter of the Greek alphabet.
Upsilon may also refer to:
Latin upsilon (Ʊ or ʊ), a Latin letter Lake Upsilon Upsilon meson (ϒ)
See also Near-close near-back rounded vowel, represented as (lowercase Latin upsilon) Ypsilon (disambiguation) Ipsilon (disambiguation) Upsilon Phi Delta Upsilon Phi Sigma Upsilon Pi Epsilon Upsilon Sigma Phi