Merry Christmas to all!

Joyeux Noël

(French)

Merry Christmas

(English)

Frohe Weihnachten

(German)

Buon Natale

(Italian)

Feliz Navidad

(Spanish)

Vrolijk Kerstfeest

(Dutch & Flemish)

Καλά Χριστούγεννα

(Greek)

Nollaig Shona Dhuit

(Gaelic)

Vesela Koleda

(Bulgarian)

Sretan Božić

(Croatian and Bosnian)

Wesołych Świąt

(Polish)

Feliz Natal

(Portuguese)

Vesele Vanoce

(Czech)

Vesele Vianoce

(Slovak)

Rõõmsaid Jõulupühi

(Estonian)

Glædelig Jul

(Danish)

Hyvää joulua

(Finnish)

Kellemes karácsonyi ünnepeket

(Hungarian)

Linksmų Kalėdų

(Lithuanian)

Priecīgus Ziemassvētkus

(Latvian)

Il-Milied it-Tajjeb

(Maltese)

Crăciun Fericit

(Romanian)

Hristos se rodi

(Serbian)

Vesel Božič

(Slovene)

God Jul

(Swedish & Norwegian)

Mutlu Noeller

(Turkish)

C рождеством!

(Russian)

Bon Nadal

(Catalan)

Bo Nadal

(Galician)

Nedeleg Laouen

(Breton)

Eguberri on

(Basque)

Schéi Chrëschtdeeg

(Luxembourgish)

Nadelik Lowen

(Cornish)

djoyeus Noyé

(Walloon)

Bon Natale

(Corsican)

Nollick Ghennal

(Manx)

Nollaig Chridheil

(Scottish Gaelic)

Nadolig Llawen

(Welsh)

Merry Christmas to all in the languages of Europe and a few endangered languages too... 

  

Sources: 

http://www.whychristmas.com/customs/languages.shtml

http://citysavvyluxembourg.com/luxembourg-life/local-culture/traditions/luxembourgs-traditions-december/ ; http://www.magakernow.org.uk/default.aspx?page=937

http://www.languagehelpers.com/words_phrases/Latvian/Learn.php?Language=Latvian&cat=37&scats=Latvian%20Translation&author=83&phraseid=185