This might be too literal of an answer but yes it will. It's a PCIEx16 video card and designed to work in any motherboard with a PCIEx16 slot. And Gigabyte is usually pretty careful about designing the boards to work with most parts. I think a more important question is will the GTX260 fit in your case.
This card is no bigger then my GTS250oc and I have this motherboard....no problem!
Like green said the case is the big factor in this.....
Umm, Johny, your off there my friend. The GTS250 is about an inch or two shorter than the 260's. Most cases can take it, but not a bottom tier mATX case. You should run a mid-size at least. It fit fine (after removing a cooling bracket) in my buds Antec 900. Best bet is to measure the cards (check the manufactures website) and measure your available room. No one likes returning things that aren't defective.