  The reciprocal degree resistance distance index of a connected graph $G$ is
defined as $RDR(G)=\sum\limits_{\{u,v\}\subseteq V(G)}\frac
{d_G(u)+d_G(v)}{r_G(u,v)}$, where $r_G(u,v)$ is the resistance distance between
vertices $u$ and $v$ in $G$. Let $\mathscr {U}_n$ denote the set of unicyclic
graphs with $n$ vertices. We study the graph with maximum reciprocal degree
resistance distance index among all graphs in $\mathscr {U}_n$, and
characterize the corresponding extremal graph.
