- "There has never been an officially funded or sanctioned development of any sort of DS Halo game."
- —Brian Jarrard
Halo DS was a proposed Halo game that would have been released on the Nintendo DS. The game was rumored throughout 2007, but was never acknowledged or developed by Bungie or Microsoft. The game never advanced beyond an unsolicited demo.
Rumors of a handheld version of Halo first surfaced in 2004 when claims that Halo would be ported to the Gameboy Advance were quickly dismissed by Microsoft.  In 2005 Microsoft again denied rumors of a handheld Halo, this time on the Gizmondo.
On January 4, 2007 Matt Casamassina of IGN claimed he had played a version of Halo for the Nintendo DS. On October 2, 2007 he demonstrated on-camera in-game footage of what he claimed was an early-development playable version of Halo DS. In a July 2007 interview with Siloconera, Bungie employees Frank O'Connor and Brian Jarrard stated, "it’s very likely that somebody at some point in time created a prototype and tried to pitch it... which is probably what Casamassina is talking about... but there has never been an officially funded or sanctioned development of any sort of DS Halo game."
The work demonstrated by Casamassina featured dual-wielding and a version of the Halo 2 map Zanzibar. The bottom screen was used mostly for the motion tracker but also had other uses, including displaying the player's weapons and shield health. Evidence including the demo's reticule, sound effects, and HUD features suggest the game was created by modding Goldeneye: Rogue Agent to serve as a proof-of-concept for the developer's pitch. Casamassina claimed it "wasn't created by a garage developer, it was actually done by a major studio, a major publisher, AAA publisher," but he did not reveal the source of the demo.