Breakfast is the most important meal of the day ... and William Shatner clearly is not about to flake on it, hauling his bowl of cereal on the road with him -- and the bran-new pics are grrreaaat!!!

The 94-year-old "Star Trek" legend was spotted at an L.A. stoplight Monday, raisin’ a spoon of what looks like Raisin Bran from a bowl in his lap, chowing down in the driver’s seat ... then casually driving off.

Despite going oat of his way for breakfast on wheels, the all-time Captain James T. Kirk didn’t look frazzled at all ... he calmly scooped up a big ol’ spoonful, opened wide, and fully enjoyed all that fiber making its grand entrance.

It’s not something you see every day ... but with his packed schedule, we don’t blame him one bit for squeezing every last moment out of breakfast.