  Accurate line lists for the carbon dimer, C$_2$, are presented. These line
lists cover rovibronic transitions between the eight lowest electronic states:
$X\,{}^{1}\Sigma_{g}^{+}$, $a\,{}^{3}\Pi_{u}$, $A\,{}^{1}\Pi_{u}$,
$b\,^{3}\Sigma_{g}^{-}$, $b\,^{3}\Sigma_{g}^{-}$, $c\,^{3}\Sigma_{u}^{+}$,
$d\,{}^{3}\Pi_{g}$, $B\,{}^{1}\Delta_{g}$, $B^\prime\,{}^{1}\Sigma_{g}^{+}$.
Potential energy curves (PECs) and transition dipole moment curves are computed
on a large grid of geometries using the aug-cc-pwCVQZ-DK/MRCI level of theory
including core and core-valence correlations and scalar relativistic energy
corrections. The same level of theory is used to compute spin-orbit and
electronic angular momentum couplings. The PECs and couplings are refined by
fitting to the empirical (MARVEL) energies of $^{12}$C$_2$ using the
nuclear-motion program Duo. The transition dipole moment curves are represented
as analytical functions to reduce the numerical noise when computing transition
line strengths. Partition functions, full line lists, Land\'{e}-factors and
lifetimes for three main isotopologues of C$_2$ ($^{12}$C$_2$,$^{13}$C$_2$ and
$^{12}$C$^{13}$C) are made available in electronic form from the CDS
(http://cdsarc.u-strasbg.fr) and ExoMol (www.exomol.com) databases.
