  We report here the first detection in the interstellar medium of the
cyanomidyl radical (HNCN). Using the Yebes 40m and the IRAM 30m telescopes, we
have targeted the doublets of the $N$=2$-$1, 4$-$3, 5$-$4, 6$-$5, and 7$-$6
transitions of HNCN toward the molecular cloud G+0.693-0.027. We have detected
three unblended lines of HNCN, these are the $N$=6$-$5 doublet and one line of
the $N$=4$-$3 transition. Additionally we present one line of the $N$=5$-$4
transition partially blended with emission from other species. The Local
Thermodynamic Equilibrium best fit to the data gives a molecular abundance of
(0.91$\pm$0.05)$\times$10$^{-10}$ with respect to H$_2$. The relatively low
abundance of this species in G+0.693-0.027, and its high reactivity, suggest
that HNCN is possibly produced by gas-phase chemistry. Our work shows that this
highly reactive molecule is present in interstellar space, and thus it
represents a plausible precursor of larger prebiotic molecules with the NCN
backbone such as cyanamide (NH$_2$CN), carbodiimide (HNCNH) and formamidine
(NH$_2$CHNH).
