I'll start.

Albanian: Grigor, Gërgur
Arabic: Jurayj (جريج) Grēgōrī (جريجوري)
Armenian: Գրիգոր (Western Armenian: Krikor; Eastern Armenian: Grigor)
Belarusian: Pыгop (Ryhor), Гpэгapы (Hrehary)
Bengali: গ্রেগরি ( Grēgari)
Bulgarian: Гpигop (Grigor)
Catalan: Gregori
Chinese: 格里高列 (Géléi gē lǐ), 格雷戈里 (Géléi gē lǐ)
Croatian: Grgur, Grga or Grgo
Czech: Řehoř
Danish: Gregers
Dutch: Gregoor, Gregorius
English: Gregory, also Gregg, Greg
Estonian: Reigo
Faroese: Grækaris
Finnish: Reijo
French: Grégory or Grégoire
Georgian: გრიგოლი (Grigoli, Grigori)
German: Gregor
Greek: Γρηγόριος (Grigorios, Gri̱górios, Gregorios), Γρηγόρης (Grigoris, Gregoris)
Gujarati: ગ્રેગરી (Grēgarī)
Hebrew: גרגורי
Hindi: ग्रेगोरी ( Grēgōrī)
Hungarian: Gergely or Gergő or Transylvanian: Gerő
Icelandic: Gregor
Indonesian: Gregorius
Irish: Gréagóir
Italian: Gregorio
Japanese: Guregori (グレゴリー)
Kannada: ಗ್ರೆಗೊರಿ, Gregori
Korean: 그레고리, Geulegoli
Latin: Gregorius
Latvian: Gregors
Lithuanian: Grigalius, Grigas or Gregoras, Gregorijus
Macedonian: Гpигopиј, Grigorij
Marathi: ग्रेगोरी (Grēgōrī)
Mongolian: Гpeгopи, Gryegori
Nepali: ग्रेगरी, Grēgarī
Norwegian: Greger or Gregers
Persian: گرگوری
Polish: Grzegorz