Particle physics (also known as high-energy physics) is the branch of physics that deals with the nature of particles that make up matter and radiation. Although the word particle can refer to a variety of small objects (e.g. protons, gas particles or even dust), particle physics deals with the smallest detectable particles and the fundamental interactions that explain their behaviour.

Particle physics is a type of quantum physics, where quantum nature, relativity and the laws of gravity are programmed into the foundations of the theory, the latter reflecting the symmetries inherent in nature. The theoretical framework used in particle physics is called quantum field theory, and the specific parameters and properties of the fields are represented by a standard model (a model is a concrete expression of a more general mathematical theory that can make predictions).