Disbeliever (noun)

1. A person who does not believe in something, often in a religious or spiritual context.
2. One who does not accept the existence of something, such as a deity or a particular doctrine.

Origin:

From dis- + believer.

Examples:

1. He was a devout disbeliever in the existence of God.
2. The politician's disbelief in climate change was widely criticized.
3. The party's disbelief in the evidence presented was a cause of concern.
4. The scientist's disbelief in the paranormal made him a target of criticism.
5. The public"s disbelief in the government"s explanation led to protests.