Not Necessarily

The answer to this question depends upon the chosen definition of “religion.” If it is understood to mean “belief in a supernatural power” then the answer is obviously “yes” and God/gods would be a necessary requirement of such a belief.

However, the term “religion” etymologically refers to a system of beliefs by which a person interprets and gives meaning to reality. This system is ultimately based on that to which a person ascribes supreme importance (or “Ultimate Concern” as it was described by Paul Tillich). For this reason, such things as consumerism, secularism, hedonism, materialism and so forth can be referred to as new “religions.”

Religious practices reflect the many ways in which people “bind” themselves to that which is of supreme importance. These expressions of commitment can include prescribed behavioral norms, esteemed virtues, doctrines, rituals, religious professions, art, and even martyrdom.

For Christians, true religion requires charity for others.