The smallest polyatomic carbon chain, C$_{3}$, has been identified in interstellar clouds (A$_{v}sim$1 mag) towards $zeta$ Ophiuchi, 20 Aquilae, and $zeta$ Persei by detection of the origin band in its $A^{1}Pi_{u}-X^{1}Sigma^{+}_{g}$ electronic transition, near 4052AA. Individual rotational lines were resolved up to $J$=30 enabling the rotational level column densities and temperature distributions to be determined. The inferred limits for the total column densities ($sim$1 to 2$times10^{12}$ cm$^{-2}$) offer a strong incentive to laboratory and astrophysical searches for the longer carbon chains. Concurrent searches for C$_2^{+}$, C$_2^{-}$ and C$_3^{-}$ were negative but provide sensitive estimates for their maximum column densities.
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