Happy Birthday in Spanish is simply said "Cumpleaños feliz". (coom-play-ahn-yos-fay-lees). A shorter and informal way to wish it is "Feliz cumple" (fay lees coom play).
Check out the video below to hear how the words to the song are pronounced.
Sung to the same tune as Happy Birthday
te deseamos (name)
There is another Happy Birthday Spanish Song, that is more traditional than the world wide version, see below...
Traditional Spanish Song
Many people in Spain actually celebrate 2 special personal days. Their birthday and their name day, also refered to as saints day. A good reason for sharing your name with a Spanish saint!
Birthday cards are not popular in Spain. A phone call from family and friends, gifts and meals out are typical ways to celebrate, but not birthday cards.
Traditionally babies were named after the saints day on the day that they were born, although this is becoming less common as a happy birthday in Spanish celebration.
Another Spanish tradition that has become very popular is the breaking of the piñata. The piñata, full of candy is hit with a stick until the candy falls out.