This chapter distinguishes between two main branches of asset pricing: (1) general equilibrium models and (2) multifactor models. We begin by reviewing the pathbreaking work by Sharpe (1964) and others, who utilized equilibrium pricing conditions in the mean-variance return world of Markowitz (1959) to derive the theoretical CAPM. Its market model form is used in empirical tests to regress excess stock returns on excess market returns (proxied by general market index returns minus Treasury bill rates) and thereby estimate beta risk coefficients. Early tests of the market model found a weaker relation between U.S. stock returns and beta than expected by the CAPM. In an attempt to overcome empirical issues in early CAPM tests, Black (1972) proposed the zero-beta CAPM as a more general form. Here we review his mathematical derivation of the zero-beta CAPM. As we will see, both of these famous models are grounded in similar portfolio theory and general equilibrium conditions. The remainder of the chapter covers various multifactor models with little or theoretical foundation but empirical support. In a series of papers, Fama and French (1992, 1993, 1995, 1996) presented convincing empirical evidence that the market model did not work for U.S. stock returns over many years and therefore declared the CAPM dead. They subsequently proposed a three-factor model that augmented the market model’s general market index with size and value multifactors, which provided a better fit to U.S. stock return data. We also discuss the following extensions of the three-factor model: Carhart’s (1997) four-factor model (adding a momentum factor), and Fama and French’s (2015) five-factor model (adding profit and capital investment factors). Lastly, we overview the Hou et al. (2015) q-factor model, Stambaugh and Yuan’s (2017) mispricing four-factor model, Fama and French’s (2018, 2020) six-factor model adding momentum to their five-factor model, and other recent model developments.