The PYTHIA 8.2 program is a standard tool for generating events in high-energy collisions, incorporating a coherent set of physics models for the evolution from a few-body hard process to a complex multiparticle final state. It includes a library of hard processes, models for initial- and final-state parton showers, matching and merging methods, multiparton interactions, beam remnants, string fragmentation, and particle decays. It also has a set of utilities and several interfaces to external programs. PYTHIA 8.2 is the second main release after the complete rewrite from Fortran to C++ and is now mature enough to replace most applications, particularly for LHC physics studies. It offers many new features that should improve the description of data. The program is intended to be self-contained for various physics studies and is also interlinked with other program packages. It uses the Les Houches Accord (LHA) and its associated Les Houches Event Files (LHEF) to combine matrix-element (ME) based calculations with PYTHIA's specialities such as initial-state radiation (ISR), final-state radiation (FSR), multiparton interactions (MPI), and string fragmentation. The physics of PYTHIA 8.2 includes a wide range of processes, such as QCD processes, electroweak processes, onia production, top production, fourth generation fermion production, Higgs processes, SUSY processes, new gauge boson processes, left-right symmetric processes, leptoquark production, compositeness processes, hidden valley processes, and extra-dimension processes. The program also includes soft processes that describe all components of the total cross section in hadronic collisions, including elastic, diffractive, and non-diffractive topologies. The parton distribution functions (PDFs) in PYTHIA 8.2 include sixteen built-in PDF sets for the proton, as well as sets for the pion, Pomeron, and leptons. The program uses LO PDFs for leading-order calculations and NLO PDFs for next-to-leading-order calculations, with the latter being less reliable for describing showers or MPIs. The parton showers in PYTHIA 8.2 are based on the dipole-style $ p_{\perp} $-ordered evolution and include new features such as $ \gamma \rightarrow q\overline{q} $ and $ \gamma \rightarrow \ell^{+}\ell^{-} $ branchings, options for emission of weak gauge bosons, and flexible colour strengths for FSR. The shower evolution is based on the standard (LO) DGLAP splitting kernels, with the overall strength of radiation set by the effective value of $ \alpha_{s}(M_{Z}) $. The multiparton interactions (MPI) in PYTHIA 8.2 are modeled using a unified framework that includes both soft and hard QCD MPI processes. The program includes aThe PYTHIA 8.2 program is a standard tool for generating events in high-energy collisions, incorporating a coherent set of physics models for the evolution from a few-body hard process to a complex multiparticle final state. It includes a library of hard processes, models for initial- and final-state parton showers, matching and merging methods, multiparton interactions, beam remnants, string fragmentation, and particle decays. It also has a set of utilities and several interfaces to external programs. PYTHIA 8.2 is the second main release after the complete rewrite from Fortran to C++ and is now mature enough to replace most applications, particularly for LHC physics studies. It offers many new features that should improve the description of data. The program is intended to be self-contained for various physics studies and is also interlinked with other program packages. It uses the Les Houches Accord (LHA) and its associated Les Houches Event Files (LHEF) to combine matrix-element (ME) based calculations with PYTHIA's specialities such as initial-state radiation (ISR), final-state radiation (FSR), multiparton interactions (MPI), and string fragmentation. The physics of PYTHIA 8.2 includes a wide range of processes, such as QCD processes, electroweak processes, onia production, top production, fourth generation fermion production, Higgs processes, SUSY processes, new gauge boson processes, left-right symmetric processes, leptoquark production, compositeness processes, hidden valley processes, and extra-dimension processes. The program also includes soft processes that describe all components of the total cross section in hadronic collisions, including elastic, diffractive, and non-diffractive topologies. The parton distribution functions (PDFs) in PYTHIA 8.2 include sixteen built-in PDF sets for the proton, as well as sets for the pion, Pomeron, and leptons. The program uses LO PDFs for leading-order calculations and NLO PDFs for next-to-leading-order calculations, with the latter being less reliable for describing showers or MPIs. The parton showers in PYTHIA 8.2 are based on the dipole-style $ p_{\perp} $-ordered evolution and include new features such as $ \gamma \rightarrow q\overline{q} $ and $ \gamma \rightarrow \ell^{+}\ell^{-} $ branchings, options for emission of weak gauge bosons, and flexible colour strengths for FSR. The shower evolution is based on the standard (LO) DGLAP splitting kernels, with the overall strength of radiation set by the effective value of $ \alpha_{s}(M_{Z}) $. The multiparton interactions (MPI) in PYTHIA 8.2 are modeled using a unified framework that includes both soft and hard QCD MPI processes. The program includes a