— Alexander the Great King of Macedon -356 - -323 avant J.-C.
Statement portrayed as a quotation in a 1927 Reader's Digest article, this probably derives from traditions about Alexander lamenting at his father Philip's victories that there would be no conquests left for him, or that after his conquests in Egypt and Asia there were no worlds left to conquer.
Some of the oldest accounts of this, as quoted by John Calvin state that on "hearing that there were other worlds, wept that he had not yet conquered one."
This may originate from Plutarch's essay On the Tranquility of Mind, part of the essays Moralia: Alexander wept when he heard Anaxarchus discourse about an infinite number of worlds, and when his friends inquired what ailed him, "Is it not worthy of tears," he said, "that, when the number of worlds is infinite, we have not yet become lords of a single one?"
There are no more other worlds to conquer!
Variant attributed as his "last words" at a few sites on the internet, but in no published sources.