"Thus we can see the two great differences between races: Aryanism means ethical perception of work and that which we today so often hear – socialism, community spirit, common good before own good. Jewry means egoistic attitude to work and thereby mammonism and materialism, the opposite of socialism. ... Socialism as the final concept of duty, the ethical duty of work, not just for oneself but also for one’s fellow man’s sake, and above all the principle: Common good before own good, a struggle against all parasitism and especially against easy and unearned income. And we were aware that in this fight we can rely on no one but our own people. We are convinced that socialism in the right sense will only be possible in nations and races that are Aryan, and there in the first place we hope for our own people and are convinced that socialism is inseparable from nationalism."
-Adolf Hitler
To be fair, yes, he was violently opposed to Marxist socialism, as he associated it with "Judeo-Bolshevism", but he was also critical of capitalism as well (again, mainly because he thought of it as "Jewish"), and supported heavy government regulation, albeit not direct ownership, of the economy. Companies had to subordinate themselves to the state, and the biggest companies of those days (IG Farben, Daimler-Benz, Krupp, etc.) all derived their power from being in bed with the state and contributing to its war effort or manufacturing gas for the concentration camps. Though he was by no means a communist, those quotes about capitalism and Lenin make me wonder if the Molotov-Ribbentrop Pact could have been feasible if Hitler didn't hold a genocidal hatred of Slavs.
In conclusion, National Socialism is a form of Socialism, but not Marxism.