  The connected coalition in a graph $G=(V,E)$ consists of two disjoint sets of
vertices $V_{1}$ and $V_{2}$, neither of which is a connected dominating set
but whose union $V_{1}\cup V_{2}$, is a connected dominating set. A connected
coalition partition in a graph $G$ of order $n=|V|$ is a vertex partition
$\psi$ = $\{V_1, V_2,..., V_k \}$ such that every set $V_i \in \psi$ either is
a connected dominating set consisting of a single vertex of degree $n-1$, or is
not a connected dominating set but forms a connected coalition with another set
$V_j\in \psi$ which is not a connected dominating set. The connected coalition
number, denoted by $CC(G)$, is the maximum cardinality of a connected coalition
partition of $G$.
  In this paper, we initiate the study of connected coalition in graphs and
present some basic results. Precisely, we characterize all graphs that have a
connected coalition partition. Moreover, we show that for any graph $G$ of
order $n$ with $\delta(G)=1$ and with no full vertex, it holds that $CC(G)<n$.
Furthermore, we show that for any tree $T$, $CC(T)=2$. Finally, we present two
polynomial-time algorithms that for a given connected graph $G$ of order $n$
determine whether $CC(G)=n$ or $CC(G)=n-1$.
