The article reviews the current status of B-meson mixing and b-hadron lifetimes from both experimental and theoretical perspectives. It discusses the potential of these observables for understanding quantum chromodynamics (QCD) and searching for effects beyond the Standard Model (SM). Updated SM predictions for mixing observables ΔM_{d,s}, ΔΓ_{d,s}, and a_{f}^{d,s} are presented. The article also outlines future prospects for theoretical and experimental improvements. B-meson lifetimes are determined by the weak decay process and are sensitive to the b-quark mass. Theoretical predictions for lifetimes are based on the heavy quark expansion (HQE), which allows for a quantitative estimation of lifetimes and lifetime ratios. Experimental measurements of lifetimes have shown good agreement with theoretical predictions, although uncertainties remain. The lifetime ratio τ(B^{+})/τ(B_{d}) has been measured and agrees with theoretical estimates. The lifetime of the Λ_b baryon has been measured with high precision, and the results are consistent with the HQE predictions. Mixing of neutral B-mesons is a macroscopic quantum effect that is suppressed in the SM. The mass difference ΔM and decay rate difference ΔΓ are key observables for studying B-meson mixing. Theoretical predictions for these observables are based on the SM and involve the calculation of box diagrams and the determination of non-perturbative matrix elements. Experimental measurements of ΔM and ΔΓ have shown good agreement with theoretical predictions, although uncertainties remain. The flavour-specific CP asymmetries a_{fs}^{d} and a_{fs}^{s} are also important observables for studying B-meson mixing. Theoretical predictions for the mass differences ΔM_{d} and ΔM_{s} are based on the SM and involve the calculation of box diagrams and the determination of non-perturbative matrix elements. Experimental measurements of ΔM_{d} and ΔM_{s} have shown good agreement with theoretical predictions, although uncertainties remain. The decay rate difference ΔΓ_{d} and ΔΓ_{s} are also important observables for studying B-meson mixing. Theoretical predictions for these observables are based on the SM and involve the calculation of box diagrams and the determination of non-perturbative matrix elements. Experimental measurements of ΔΓ_{d} and ΔΓ_{s} have shown good agreement with theoretical predictions, although uncertainties remain. The article also discusses the potential for BSM effects in B-meson mixing and lifetimes. These effects could lead to deviations from SM predictions and provide insights into new physics. The current experimental and theoretical status of B-meson mixing and lifetimes is summarized, and future prospects for improvements are outlined.The article reviews the current status of B-meson mixing and b-hadron lifetimes from both experimental and theoretical perspectives. It discusses the potential of these observables for understanding quantum chromodynamics (QCD) and searching for effects beyond the Standard Model (SM). Updated SM predictions for mixing observables ΔM_{d,s}, ΔΓ_{d,s}, and a_{f}^{d,s} are presented. The article also outlines future prospects for theoretical and experimental improvements. B-meson lifetimes are determined by the weak decay process and are sensitive to the b-quark mass. Theoretical predictions for lifetimes are based on the heavy quark expansion (HQE), which allows for a quantitative estimation of lifetimes and lifetime ratios. Experimental measurements of lifetimes have shown good agreement with theoretical predictions, although uncertainties remain. The lifetime ratio τ(B^{+})/τ(B_{d}) has been measured and agrees with theoretical estimates. The lifetime of the Λ_b baryon has been measured with high precision, and the results are consistent with the HQE predictions. Mixing of neutral B-mesons is a macroscopic quantum effect that is suppressed in the SM. The mass difference ΔM and decay rate difference ΔΓ are key observables for studying B-meson mixing. Theoretical predictions for these observables are based on the SM and involve the calculation of box diagrams and the determination of non-perturbative matrix elements. Experimental measurements of ΔM and ΔΓ have shown good agreement with theoretical predictions, although uncertainties remain. The flavour-specific CP asymmetries a_{fs}^{d} and a_{fs}^{s} are also important observables for studying B-meson mixing. Theoretical predictions for the mass differences ΔM_{d} and ΔM_{s} are based on the SM and involve the calculation of box diagrams and the determination of non-perturbative matrix elements. Experimental measurements of ΔM_{d} and ΔM_{s} have shown good agreement with theoretical predictions, although uncertainties remain. The decay rate difference ΔΓ_{d} and ΔΓ_{s} are also important observables for studying B-meson mixing. Theoretical predictions for these observables are based on the SM and involve the calculation of box diagrams and the determination of non-perturbative matrix elements. Experimental measurements of ΔΓ_{d} and ΔΓ_{s} have shown good agreement with theoretical predictions, although uncertainties remain. The article also discusses the potential for BSM effects in B-meson mixing and lifetimes. These effects could lead to deviations from SM predictions and provide insights into new physics. The current experimental and theoretical status of B-meson mixing and lifetimes is summarized, and future prospects for improvements are outlined.