This paper presents a comprehensive database of atomic and molecular data for use in radiative transfer modeling of submillimetre and infrared observations. The database includes energy levels, statistical weights, Einstein A-coefficients, and collisional rate coefficients for 23 molecular species, as well as three atomic species. The data are publicly available at http://www.strw.leidenuniv.nl/~moldata and are essential for non-LTE line radiative transfer programs. An online version of the RADEX code, which performs statistical equilibrium calculations, is also provided. The database includes extrapolated collisional rate coefficients to higher energies (up to E/k ~ 1000 K), which are necessary for accurate modeling of astrophysical conditions. The database is designed to be used in radiative transfer modeling of interstellar regions and includes data for rotational transitions in the ground vibrational state, with vibrational levels included for some common species. The database also includes hyperfine splitting data for some molecules. The collisional rate coefficients are derived from theoretical calculations and experimental data, with uncertainties discussed. The database is intended to be a valuable tool for analyzing observations from current and future (sub)millimetre and infrared telescopes. The paper also discusses the importance of accurate molecular data in determining physical and chemical conditions in astrophysical objects, and highlights the need for further efforts in providing such data. The database is a first step in systematically collecting and presenting data for radiative transfer modeling of interstellar regions.This paper presents a comprehensive database of atomic and molecular data for use in radiative transfer modeling of submillimetre and infrared observations. The database includes energy levels, statistical weights, Einstein A-coefficients, and collisional rate coefficients for 23 molecular species, as well as three atomic species. The data are publicly available at http://www.strw.leidenuniv.nl/~moldata and are essential for non-LTE line radiative transfer programs. An online version of the RADEX code, which performs statistical equilibrium calculations, is also provided. The database includes extrapolated collisional rate coefficients to higher energies (up to E/k ~ 1000 K), which are necessary for accurate modeling of astrophysical conditions. The database is designed to be used in radiative transfer modeling of interstellar regions and includes data for rotational transitions in the ground vibrational state, with vibrational levels included for some common species. The database also includes hyperfine splitting data for some molecules. The collisional rate coefficients are derived from theoretical calculations and experimental data, with uncertainties discussed. The database is intended to be a valuable tool for analyzing observations from current and future (sub)millimetre and infrared telescopes. The paper also discusses the importance of accurate molecular data in determining physical and chemical conditions in astrophysical objects, and highlights the need for further efforts in providing such data. The database is a first step in systematically collecting and presenting data for radiative transfer modeling of interstellar regions.