The paper presents a theory of natural electroweak symmetry breaking, generalizing an approach based on deconstruction. This theory is the smallest extension of the Standard Model to date that stabilizes the electroweak scale with a naturally light Higgs and weakly coupled new physics at TeV energies. The Higgs is one of a set of pseudo-Goldstone bosons in an $SU(5)/SO(5)$ nonlinear sigma model, with the symmetry breaking scale $f$ around a TeV and a cutoff $\Lambda \leq 4\pi f \sim 10$ TeV. A single electroweak doublet, the "little Higgs," is automatically much lighter than other pseudo-Goldstone bosons. The quartic self-coupling for the little Higgs is generated by gauge and Yukawa interactions, while the top Yukawa coupling triggers electroweak symmetry breaking. The effective theory below the TeV scale is the minimal Standard Model, with additional particles at the TeV scale including spin one bosons, an electroweak singlet quark, and an electroweak triplet scalar. One-loop quadratically divergent corrections to the Higgs mass are canceled by interactions with these additional particles. The model is designed to be economical, with only a small number of new degrees of freedom, and it provides a natural framework for understanding electroweak symmetry breaking without fine-tuning.The paper presents a theory of natural electroweak symmetry breaking, generalizing an approach based on deconstruction. This theory is the smallest extension of the Standard Model to date that stabilizes the electroweak scale with a naturally light Higgs and weakly coupled new physics at TeV energies. The Higgs is one of a set of pseudo-Goldstone bosons in an $SU(5)/SO(5)$ nonlinear sigma model, with the symmetry breaking scale $f$ around a TeV and a cutoff $\Lambda \leq 4\pi f \sim 10$ TeV. A single electroweak doublet, the "little Higgs," is automatically much lighter than other pseudo-Goldstone bosons. The quartic self-coupling for the little Higgs is generated by gauge and Yukawa interactions, while the top Yukawa coupling triggers electroweak symmetry breaking. The effective theory below the TeV scale is the minimal Standard Model, with additional particles at the TeV scale including spin one bosons, an electroweak singlet quark, and an electroweak triplet scalar. One-loop quadratically divergent corrections to the Higgs mass are canceled by interactions with these additional particles. The model is designed to be economical, with only a small number of new degrees of freedom, and it provides a natural framework for understanding electroweak symmetry breaking without fine-tuning.