The whole concept of pure blood is delusional. While the answer is a definitive yes, understanding the nuances of his lineage and how it shaped. The canon evidence is not conclusive.
Did The Death Eaters Know Voldemort Was Half Blood? Did They Know He
They ignore it but don't like people to remind that voldemort is half blood like bellatrix in ootp.
Here's the quote from chapter 35, harry speaking to death eaters in the dept.
As hagrid says, there isn't a witch or wizard. There may have been some side chatter among death eaters about it, but by then, the aura and power of voldemort was enough for them to ignore that and accept him as their master. He once again declares war,. Families like the malfoys were more than willing to serve lord voldemort, whose father was a muggle (not even.
