No. Satanists are a group who believe mostly in human nature. Contrary to popular belief, they do not worship Satan. They do not believe in Satan, heaven, hell, or God.
This is the definition from Wikipedia in italics: Satanism is a term that refers to a number of related belief systems. Their commonality is that they all feature the symbolism of Satan (or similar figures) which originated as a challenging role within Judaism (in The Book of Job), and developed within Christian mythology into a cosmological adversary.There are two primary forms of Satanism; Theistic Satanism and LaVeyan Satanism. Theistic Satanists believe that Satan is a real being with existence, whom adherents venerate as a deity or entity with whom to cooperate. Some, though not all, theistic Satanists consider Satan to be benevolent. LaVeyan Satanism[1], in contrast, is atheistic. These latter Satanists believe that Satan is merely symbolic of humanity's carnal nature.Because some Satanists actively worship Satan, believing him to be a real deity, they could be viewed as being a Christian denomination[2].It is often the practice of any given Satanist not to refer to themselves with a hyphenated prefix. Each "type" of Satanist will usually refer to themselves only as "Satanist".
Christian religion is the belief and worship of Christ, as the word implies. Therefore, Satanism is the belief and worship of Satan, the fallen angel. I disagree with Wiki's definition as since whoever wrote that part believes that Satan "to be a real deity, they could be viewed as being a Christian denomination". To be a Christian denomination, you must have Christ as your central point of worship. Point in case, Buddhist worship Buddha, Muslims worship Mohammed, etc., you get the picture.
Satanism, by the aforementioned definition and most others, is the worship of Satan as a deity. Christians do not worship Satan or 'venerate [him] as a deity or entity with whom to cooperate'. Neither do Christians see Satan as benevolent. Therefore, Satanism would be hard pressed to fit into Christianity by that definition. As for LaVeyan Satanism, Christianity is not by definition 'atheistic', so Satanism certainly doesn't qualify under that definition either. A Satanist does not worship God or accept Christ as Saviour, two defining characteristics of Christianity. Satanism, therefore, is not a Christian religion. The point on which both camps would agree is that Satan is a valid being. However, believing in the existence of a being is not the same as adhering to the beliefs which define that religion.