The strontium gallium oxynitride Sr4GaN3O and nitride-carbodiimide Sr4GaN3(CN2) are reported, synthesized as single crystals from molten sodium at 900 degrees C. Red Sr4GaN3O crystallizes in space group Pbca (No. 61) with a = 7.4002(1) angstrom, b = 24.3378(5) angstrom, c = 7.4038(1) angstrom, and Z = 8, as determined from single-crystal X-ray diffraction measurements at 150 K. The structure may be viewed as consisting of slabs [Sr4GaN3](2+) containing double layers of isolated [GaN3](6-) triangular anions arranged in a "herringbone" fashion, and these slabs are separated by O2- anions. Brown Sr4GaN3(CN2) has a closely related structure in which the oxide anions in the Sr4GaN3O structure are replaced by almost linear carbodiimide [CN2](2-) anions [Sr4GaN3(CN2): space group P2(1)/c (No. 14), a = 13.4778-(2) angstrom, b = 7.4140(1) angstrom, c = 7.4440(1) angstrom, beta = 98.233(1)degrees, and Z = 4].