  We consider an inhomogeneous Erd\H{o}s-R\'enyi random graph $G_N$ with vertex
set $[N] = \{1,\dots,N\}$ for which the pair of vertices $i,j \in [N]$, $i\neq
j$, is connected by an edge with probability $r_N(\tfrac{i}{N},\tfrac{j}{N})$,
independently of other pairs of vertices. Here, $r_N\colon\,[0,1]^2 \to (0,1)$
is a symmetric function that plays the role of a reference graphon. Let
$\lambda_N$ be the maximal eigenvalue of the Laplacian matrix of $G_N$. We show
that if $\lim_{N\to\infty} \|r_N-r\|_\infty = 0$ for some limiting graphon
$r\colon\,[0,1]^2 \to (0,1)$, then $\lambda_N/N$ satisfies a downward LDP with
rate $\binom{N}{2}$ and an upward LDP with rate $N$. We identify the associated
rate functions $\psi_r$ and $\widehat{\psi}_r$, and derive their basic
properties.
