We describe the use of the cluster regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) system (CRISPR/Cas) system involving RNA-guided endonucleases to introduce specific mutations in rice and wheat. For four rice genes and one wheat gene, the frequencies of sgRNA:Cas9 induced mutations were 14.5 to 38.0% in protoplasts, and 4.0 to 9.4% in regenerated rice plants. We also demonstrate homology-directed targeted gene modification in rice using a single-stranded DNA (ssDNA) oligo as a donor template. Our findings establish that the sgRNA:Cas9 system can be used for rice and wheat genome modification, the first plants shown to be amenable to this gene editing approach.