万有理论（英语：Theory of Everything或ToE）指的是假定存在的一种具有总括性、一致性的物理理论框架，能够解释宇宙的所有物理奥秘。经过几个世纪奋勉不懈的努力，发展出两种理论框架：广义相对论与量子场论。它们的总合，可以说是最接近想像中的万有理论。广义相对论专注于研究引力来明白宇宙的大尺度与高质量现象，例如恒星、星系、星系团等等。量子场论专注于研究非引力来明白宇宙的小尺度与低质量现象，例如，亚原子粒子、原子、分子等等。量子场论成功地给出标准模型，并且能够按照大统一理论将弱力、强力与电磁力这三种非引力统合在一起。

A theory of everything (ToE) or final theory, ultimate theory, or master theory is a hypothetical single, all-encompassing, coherent theoretical framework of physics that fully explains and links together all physical aspects of the universe. Finding a ToE is one of the major unsolved problems in physics. Over the past few centuries, two theoretical frameworks have been developed that, as a whole, most closely resemble a ToE. These two theories upon which all modern physics rests are general relativity (GR) and quantum field theory (QFT). GR is a theoretical framework that only focuses on gravity for understanding the universe in regions of both large-scale and high-mass: stars, galaxies, clusters of galaxies, etc. On the other hand, QFT is a theoretical framework that only focuses on three non-gravitational forces for understanding the universe in regions of both small scale and low mass: sub-atomic particles, atoms, molecules, etc. QFT successfully implemented the Standard Model and unified the interactions (so-called Grand Unified Theory) between the three non-gravitational forces: weak, strong, and electromagnetic force.