Yes, That is a Real $5 Bill

The Federal Reserve Board is placing a new $5 bill into circulation today. This newly designed currency incorporates new security features.

If you hold the new $5 bill to the light, you'll see a new watermark and a security thread. Here is a description from the FRB of these new features:

• Watermarks: There are now two watermarks on the redesigned $5 bill. A large number "5" watermark is located in a blank space to the right of the portrait replacing the previous watermark portrait of President Lincoln found on the older-design $5 bills. A second watermark -- a column of three smaller “5”s -- has been added to the new $5 bill design and is positioned to the left of the portrait.
  
• Security Thread: The embedded security thread runs vertically and is now located to the right of the portrait on the redesigned $5 bill. The letters "USA" followed by the number "5" in an alternating pattern are visible along the thread from both sides of the bill. The thread glows blue when held under ultraviolet light.
  

The MoneyFactory is a website from the Bureau of Engraving and Printing. This site has images and excellent descriptions of the new bill.