S50

S50, S-50, or S.50 may refer to:
 * S-50 (Manhattan Project), a uranium enrichment project of the Manhattan Project
 * USS S-50 (SS-161), a United States Navy submarine in commission from 1922 to 1927
 * Marchetti MVT or SIAI S.50, an Italian fighter of 1919
 * Letov Š-50, a Czechoslovakian Letov aircraft