Yes, and we are a part of it!
The term « pagan » applies to a variety of pre-Christian, nature-oriented religious traditions. Pagan religions are typically polytheistic, but it is possible for a person to treat the pagan gods as metaphors and not really existing. This is no different from treating the pagan stories as metaphors rather than real events, something that is even more common. If a pagan doesn’t believe that the gods in their tradition are real, then they will probably be an atheist. Some may eschew this label, but others are comfortable with it and openly identify as pagan atheists (or atheistic pagans).
The Sanskrit word nirisvaravada translates at atheism and means disbelief in a creator god. It does not require disbelief in anything else that might be a « god, » but for many anything less than a creator isn’t a genuine god in the first place. Both the Samkhya and the Mimamsa schools of Hindu philosophy reject the existence of a creator god, making them explicitly atheistic from a Hindu perspective. This doesn’t make them naturalistic, but it does make them as atheistic as any belief system, philosophy, or religion from the perspective of religious theists in the West.
Buddhism is widely regarded as an atheistic religion. Buddhist scriptures either do not promote or actively reject the existence of a creator god, the existence of « lesser » gods who are the source of morality and that humans owe any duties to any gods. At the same time, though, these scriptures accept the existence of supernatural beings which might be described as gods. Some Buddhists today believe in the existence of such beings and are theists. Others dismiss these beings and are atheists. Since there is nothing about Buddhism which requires a belief in gods, atheism in Buddhism is easy to maintain.
For Jains, every soul or spiritual being is worthy of the exact same praise. Because of this, Jains do not worship any « higher » spiritual beings like gods nor do they worship or pay homage to any idols. Jains believe that the universe has always existed and will always exist, so there is no need for any sort of creator god. None of this means that no spiritual beings exist which might be called « gods, » however, and thus a Jain might believe in beings which might be considered gods and therefore technically be a theist. From a Western religious perspective, though, they’d all be atheists.
Confucian and Taoist Atheism
On a functional level, at least, both Confucianism and Taoism can be considered atheistic. Neither is founded on faith in a creator god like Christianity and Islam are. Neither promotes the existence of such a god, either. Confucian texts describe a « Heaven » which is a transcendent, personal power of some sort. Whether this qualifies as a personal deity or not is a subject of debate, but it seems at least possible for a person to follow Confucian teachings and be an atheist. Basically, the same issue exists for Taoism: belief in some deity may be included, but may not be absolutely required.
Judaism is a religion founded upon a belief in a single creator god; it’s one of the oldest and earliest forms of monotheism known. Today, however, there are Jews who have rejected belief in this god while retaining attributes of Judaism as possible. In some cases, people have retained very little and call themselves Jews for ethnic reasons. Others retain a great deal of Jewish traditions and call themselves Jews not just from a cultural, but also from a religious perspective. They consider themselves every bit as religious as the Jews who continue to believe in God.
As a descendant of Judaism, Christianity is also a religion founded upon a belief in a single creator god. Atheism is not just rejected, but considered a sin. There are a few people who consider themselves Christians even though they have rejected belief in the existence of any gods, including the Christian creator god. They argue that they are Christian atheists in the same way that some Jews are also atheists: they are Christian for largely cultural reasons, but continue to maintain some religious observances — just without references to any gods.
Modern Paranormal Religions & Atheism
Scientology has little to say on the subject of gods. It « acknowledges » the existence of a single creator god, but doesn’t teach anything specific about it and allows members to worship as they see fit. It may thus be possible for a Scientologist to not worship and not believe. Raelians are explicitly and even « militantly » atheist, in the sense that atheism and freedom for atheists are aggressively pursued. Other modern UFO religions, based around belief in aliens rather than supernatural beings like gods, also at least allow for atheism if not openly endorse atheism as more scientific and rational than theism.
Humanistic, Naturalistic Religions & Atheism
There are humanistic religious groups today which endorse belief systems that focus on the needs of human beings here and now while rejecting (or at least minimizing) supernatural beliefs generally. A significant percentage of the members of Unitarian Universalist churches are atheists, though these churches also include Christians, pagans, and others. Members of Ethical Culture groups may or may not believe in any gods; some don’t even regard Ethical Culture as being a religious group for themselves though it is considered a religion under the law. Religious humanism creates a religious context without gods.