Happy Birthday in Japanese

tanjoubi is the japanese word for birthday and omedeto is the word for congratulations.

Polite form

o tanjoubi omedtou gozaimasu [お誕生日おめでとうございます]

o - (polite form)
tanjoubi [誕生日] - birthday
omedeto [おめでとう] - congratulations
gozaimasu [ございます] - (polite form)

tanjoubi omedtou [誕生日おめでとう]

ハッピーバースデー (happy bazde)

happy bazde is a borrowed word from the English world Happy Birthday and is mostly used among the younger Japanese.