Simon III may refer to:

Simon III, Count of Saarbrücken (c. 1180–1243) Simon III, Count of Sponheim-Kreuznach (>1330–1414) Simon III, Lord of Lippe (c. 1340–1410) Simon III of Isenburg-Kempenich (ruled 1367–1420) Simon III Gurieli (died 1792), Georgian Prince of Guria 1788–1792