+ Estonian, Karelian, Latgalian, Latvian, Livonian, Liivi Karelian, Russian, Veps, Votic, Võro
As has already been mentioned, there are some differences among the words in terms of thickness, chunkiness, types of fruit, etc.
Dutch: jam
English: jam
German: Marmelade, officially Konfitüre for most fruits and berries
Icelandic: sulta
Luxembourgish: Gebeess
Norwegian: syltetøy
Rhine Franconian (Saarbrücken dialect): Sißschmier ("sweet spread"), separate words exists for some kinds of jam
Catalan: melmelada, confitura
French: marmelade, confiture
Italian: marmellata, confettura (I think the difference is that the latter contains fruit pieces)
Occitan: mermelada, confidura, confimenta
Portuguese: geleia, compota, doce, marmelada [only if made out of quinces]
Spanish: mermelada, dulce (note: "dulce" also means "sweet" in general)
Latgalian: vuoreklis
Latvian: ievārījums / zapte
Lithuanian: uogienė
Bulgarian: сладко, конфитюр, мармалад
Polish: dżem, konfitury (=dżemy, plural of 'dżem'), marmolada (=dżem śliwkowy 'plum jam')
Russian: варенье
Serbian: џем, пекмез, мармелада [džem, pekmez, marmelada] (there's some difference between them but I dont know what. I think џем is thicker and more dense than пекмез)
Slovenian: marmelada, džem (the difference is that there are pieces of fruit in džem)
Ukrainian: варення, джем [varennja, dzhem]
Scots-Gaelic: silidh
Estonian: moos / džemm
Finnish: hillo
Hungarian: lekvár ('dzsem' is also widely understood, but much less used)
Karelian: vareńńa
Livonian: zapt
Liivi Karelian: vareńńu
Veps: marjkeitoz
Votic: varenja / vareńńa
Võro: sahvť / muuś
Turkish: Reçel
Chinese: 果酱 (果醬) [guǒjiàng]
Inuktitut: jaama (N Baffin), jaamak/jilik (Labrador), marmilaaji (W Greenland), mamalaajaq (E Greenland) = butter/jam-spread
Esperanto: marmelado, konfitaĵo