Yes, but that was after years of occupation but Austria, Russia, and Prussia/Germany. I'm looking for Poland to never be under all out occupation and to remain independent and powerful for most, if not all its history.
What? Russia didn't exist at a time, and Prussia was a Polish vassal.
Possible PoDs:
12th century - No feudal fragmentation by Boleslaw III Wrymouth - this can keep early medieval Poland united, most likely keeping Silesia and Pomerania. Standing better chances against Mongols, and butterflying away Teutonic Order (and thus, German Prussia).
13th century - victory or survival of Henry the Pious at battle of Legnica. This would likely result in reunited Poland, led by Silesian Piasts, that would be stronger than OTL pre-Lithuanian Union Poland. Possible involvement within HRE.
15th century - ongoing Jagiellonian personal union with Hungary, possibly Bohemia. Poland+Lithuania+Hungary+Bohemia would be quite strong 'blob'.
16th century - centralisation of power by Jagiellonians, and no Rzeczpospolita. Without parasitic effect of inflating noble priviledges, P-L would remain strong, dispelling partitions.
17th century - centralisation of power by Wasas, more successful meddling in Russia during Times of Trouble. Crippling Russia wouldn't solve the problems of growing political backwardness due to 'noble anarchy', but without Russia there would be no partitions.
18th century - very tricky, a bit too late for Poland to remain strong player.