The chapter discusses the salient features of CP-violating interactions in the Standard Model of electroweak interactions and its extensions, particularly multi-Higgs and supersymmetric models. It highlights the role of the Kobayashi-Maskawa (KM) mechanism in CP violation, which is related to the mixing of quark generations and the hierarchy of quark masses. The strong CP problem, which involves the QCD vacuum angle, is also addressed, noting that a non-zero QCD vacuum angle would require fine-tuning to be consistent with experimental data. The chapter explores explicit and spontaneous CP violation in various extensions of the Standard Model, including multi-Higgs models and supersymmetric models. In multi-Higgs models, CP violation can arise from the Higgs potential or charged Higgs boson exchanges, leading to CP effects in flavor-diagonal amplitudes. In supersymmetric models, CP violation can come from soft supersymmetry breaking terms, Yukawa interactions, and the Higgs potential. Spontaneous CP violation in the early universe is discussed, including the cosmological implications and the possibility of CP violation in the baryon asymmetry of the universe. The chapter also reviews experimental searches for CP violation in weak decays of kaons, hyperons, charm, and beauty particles, as well as searches for permanent electric dipole moments (EDMs) in particles and atoms. These searches are crucial for testing the KM mechanism and identifying new CP-violating interactions.The chapter discusses the salient features of CP-violating interactions in the Standard Model of electroweak interactions and its extensions, particularly multi-Higgs and supersymmetric models. It highlights the role of the Kobayashi-Maskawa (KM) mechanism in CP violation, which is related to the mixing of quark generations and the hierarchy of quark masses. The strong CP problem, which involves the QCD vacuum angle, is also addressed, noting that a non-zero QCD vacuum angle would require fine-tuning to be consistent with experimental data. The chapter explores explicit and spontaneous CP violation in various extensions of the Standard Model, including multi-Higgs models and supersymmetric models. In multi-Higgs models, CP violation can arise from the Higgs potential or charged Higgs boson exchanges, leading to CP effects in flavor-diagonal amplitudes. In supersymmetric models, CP violation can come from soft supersymmetry breaking terms, Yukawa interactions, and the Higgs potential. Spontaneous CP violation in the early universe is discussed, including the cosmological implications and the possibility of CP violation in the baryon asymmetry of the universe. The chapter also reviews experimental searches for CP violation in weak decays of kaons, hyperons, charm, and beauty particles, as well as searches for permanent electric dipole moments (EDMs) in particles and atoms. These searches are crucial for testing the KM mechanism and identifying new CP-violating interactions.