The highly selective conversion of nitrite to N2 at a quasi-perfect Pt(100) electrode in alkaline media was investigated with a particular emphasis on its structure sensitivity and its mechanism. High-quality (100) terraces are required to optimize the catalytic activity and steer the selectivity to N2: defects of any symmetry dramatically reduce the N2 evolution at [(100) × (110)] and [(100) × (111)] surfaces. On the other hand, nitrite reduction proves to be an additional example of the unique intrinsic ability of (100) surfaces to catalyze reactions involving bond breaking and successive bond formation. In the present case, (100) is able to reduce nitrite to NH2,ads, which in a certain potential window combines with NOads to give N2 in a Langmuir-Hinshelwood reaction. Our findings are similar to those for other processes generating N2, from bacterial anoxic ammonia oxidation ("anammox") to the high-temperature NO + NH3 reaction at Pt(100) crystals under ultra-high-vacuum conditions, thus suggesting that the combination of these two nitrogen-containing species is a universal (low-temperature) pathway to N2. The advantages of this pathway over other N2-generating pathways are pointed out.