This paper explores the implications of extra-dimensional axions, which arise as modes of higher-dimensional gauge fields, and their potential role in solving the Strong CP problem. The author argues that these axions are not pseudo-Nambu-Goldstone bosons (PNGBs) of a 4d symmetry but rather fundamental objects whose tension is at or above the quantum gravity cutoff scale. The axion decay constant f is expected to be related to the fundamental cutoff scale, with f being at most two orders of magnitude below it. The paper provides a self-contained introduction to extra-dimensional axions, their couplings to gauge fields, instantons, and axion strings. It also discusses the qualitative features of extra-dimensional axions, including their massless nature, their interactions with gauge fields, and their role in cosmology. The paper emphasizes that the axion decay constant is a guide to the fundamental UV cutoff of the theory, and that the tension of axion strings is expected to be of the order 2πS_instf², where S_inst is the instanton action. The paper also discusses the relationship between axion physics and chiral fermions, and concludes with a discussion of future directions and open questions in the field.This paper explores the implications of extra-dimensional axions, which arise as modes of higher-dimensional gauge fields, and their potential role in solving the Strong CP problem. The author argues that these axions are not pseudo-Nambu-Goldstone bosons (PNGBs) of a 4d symmetry but rather fundamental objects whose tension is at or above the quantum gravity cutoff scale. The axion decay constant f is expected to be related to the fundamental cutoff scale, with f being at most two orders of magnitude below it. The paper provides a self-contained introduction to extra-dimensional axions, their couplings to gauge fields, instantons, and axion strings. It also discusses the qualitative features of extra-dimensional axions, including their massless nature, their interactions with gauge fields, and their role in cosmology. The paper emphasizes that the axion decay constant is a guide to the fundamental UV cutoff of the theory, and that the tension of axion strings is expected to be of the order 2πS_instf², where S_inst is the instanton action. The paper also discusses the relationship between axion physics and chiral fermions, and concludes with a discussion of future directions and open questions in the field.