Other than the Santa costumes, the next most popular Christmas fancy dress costume are the Santa's little helpers: elf costumes
Traditionally Christmas Elves have a red or yellow and green costume with pointy ears, long noses, and pointy hats. Despite having similar names, Christmas elfs and fantasy elves are not the same species. Christmas elfs are actually more similar to pixies and gnomes than fantasy elves. I think people mistakenly believe that elfs and elves are the same race comes from Santa's elfs being referred to as "Santa's elves"
Whatever the case the Christmas elf costume pictured is probably the best known elf outfit for sale at the moment which you will probably find in most decent fancy dress shops and on-line retailers and comes with the elf hat, coat, trousers, belt, and boots.
To buy any of the Christmas Elf costumes on this page, as well as many other elf costumes, there are a few links below that may help you:
Christmas Elf Costumes on Amazon.com
Christmas Elf Costumes on BuyCostumes.com
Elf Costumes & Free shipping on orders at Costumekingdom.com
Christmas Elf Costumes on Amazon.co.uk
Sexy Elf Costumes
Female Elf Costume are also popular and there are quite a few very sexy elf costumes available. The deluxe sexy elf costume pictured is not cheap but is well made and comes with the bell-tipped hat and dress with belt and green-striped stockings.
Childrens Elf Costumes
Again there are plenty of outfits to choose from for children, for both boys and girls.
Baby elf Costume
One of the cutest fancy dress costumes for Christmas has to be this Baby Bunting Elf Costume from Smiffys.
If you would rather make your own here is an article on How to Make a Christmas elf costume