English - I love you
Afrikaans - Ek het jou lief
Albanian - Te dua
Arabic - Ana behibak (to male)
Arabic - Ana behibek (to female)
Armenian - Yes kez sirumem
Bambara - M'bi fe
Bengali - Ami tomake bhalobashi (pronounced: Amee toe-ma-kee bhalo-bashee)
Belarusian - Ya tabe kahayu
Bisaya - Nahigugma ako kanimo
Bulgarian - Obicham te
Cambodian - Soro lahn nhee ah
Catalan - T'estimo
Cherokee - Tsi ge yu i
Cheyenne - Ne mohotatse
Chichewa - Ndimakukonda
Chinese
Cantonese - Ngo oiy ney a
Mandarin - Wo ai ni
Comanche - U kamakutu nu
(pronounced oo----ka-ma- koo-too-- ---nu) -- Thx Tony
Corsican - Ti tengu caru (to male)
Cree - Kisakihitin
Creol - Mi aime jou
Croatian - Volim te
Czech - Miluji te
Danish - Jeg Elsker Dig
Dutch - Ik hou van jou
Elvish - Amin mela lle (from The Lord of The Rings, by J.R.R. Tolkien)
Esperanto - Mi amas vin
Estonian - Ma armastan sind
Ethiopian - Afgreki'
Faroese - Eg elski teg
Farsi - Doset daram
Filipino - Mahal kita
Finnish - Mina rakastan sinua
French - Je t'aime, Je t'adore
Frisian - Ik hald fan dy
Gaelic - Ta gra agam ort
Georgian - Mikvarhar
German - Ich liebe dich
Greek - S'agapo
Gujarati - Hoo thunay prem karoo choo
Hiligaynon - Palangga ko ikaw
Hawaiian - Aloha Au Ia `oe
Hebrew
To female - "ani ohev otach" (said by male) "ohevet Otach" (said by female)
To male - "ani ohev otcha" (said by male) "Ohevet ot'cha" (said by female)
Hiligaynon - Guina higugma ko ikaw
Hindi - Hum Tumhe Pyar Karte hae
Hmong - Kuv hlub koj
Hopi - Nu' umi unangwa'ta
Hungarian - Szeretlek
Icelandic - Eg elska tig
Ilonggo - Palangga ko ikaw
Indonesian - Saya cinta padamu
Inuit - Negligevapse
Irish - Taim i' ngra leat
Italian - Ti amo
Japanese - Aishiteru or Anata ga daisuki desu
Kannada - Naanu ninna preetisuttene
Kapampangan - Kaluguran daka
Kiswahili - Nakupenda
Konkani - Tu magel moga cho
Korean - Sarang Heyo or Nanun tangshinul sarang hamnida
Latin - Te amo
Latvian - Es tevi miilu
Lebanese - Bahibak
Lithuanian - Tave myliu
Luxembourgeois - Ech hun dech gaer
Macedonian - Te Sakam
Malay - Saya cintakan mu / Aku cinta padamu
Malayalam - Njan Ninne Premikunnu
Maltese - Inhobbok
Marathi - Me tula prem karto
Mohawk - Kanbhik
Moroccan - Ana moajaba bik
Nahuatl - Ni mits neki
Navaho - Ayor anosh'ni
Ndebele - Niyakutanda
Norwegian
Bokmaal - Jeg elsker deg
Nyonrsk - Eg elskar deg
Pandacan - Syota na kita!!
Pangasinan - Inaru Taka
Papiamento - Mi ta stimabo
Persian - Doo-set daaram
Pig Latin - Iay ovlay ouyay
Polish - Kocham Ciebie
Portuguese - Eu te amo
Romanian - Te iubesc
Russian - Ya tebya liubliu
Scot Gaelic - Tha gra\dh agam ort
Serbian - Volim te
Setswana - Ke a go rata
Sign Language - ,\,,/ (represents position of fingers when signing 'I Love You')
Sindhi - Maa tokhe pyar kendo ahyan
Sioux - Techihhila
Slovak - Lu`bim ta
Slovenian - Ljubim te
Spanish - Te quiero / Te amo
Swahili - Ninapenda wewe
Swedish - Jag alskar dig
Swiss-German - Ich lieb Di
Surinam - Mi lobi joe
Tagalog - Mahal kita
Taiwanese - Wa ga ei li
Tahitian - Ua Here Vau Ia Oe
Tamil - Nan unnai kathalikaraen
Telugu - Nenu ninnu premistunnanu
Thai
To female - Phom rak khun
To male - Chan rak khun
Informal - Rak te
Tunisian - Ha eh bak
Turkish - Seni Seviyorum
Ukrainian - Ya tebe kahayu
Urdu - mai aap say pyaar karta hoo
Vietnamese
To female - Anh ye^u em
To male - Em ye^u anh
Welsh - 'Rwy'n dy garu di  
Yiddish - Ikh hob dikh
Yoruba - Mo ni fe
Zazi - Ezhele hezdege
Zuni - Tom ho' ichema