The detection of intracellular microbial DNA is critical to appropriate innate immune responses; however, knowledge of how such DNA is sensed is limited. Here we identify IFI16, a PYHIN protein, as an intracellular DNA sensor that mediates the induction of interferon-beta (IFN-beta). IFI16 directly associated with IFN-beta-inducing viral DNA motifs. STING, a critical mediator of IFN-beta responses to DNA, was recruited to IFI16 after DNA stimulation. Lowering the expression of IFI16 or its mouse ortholog p204 by RNA-mediated interference inhibited gene induction and activation of the transcription factors IRF3 and NF-kappaB induced by DNA and herpes simplex virus type 1 (HSV-1). IFI16 (p204) is the first PYHIN protein to our knowledge shown to be involved in IFN-beta induction. Thus, the PYHIN proteins IFI16 and AIM2 form a new family of innate DNA sensors we call 'AIM2-like receptors' (ALRs).