  We study an analogue of the Erd\H{o}s-S\'os forbidden intersection problem,
for families of linear maps. If $V$ and $W$ are vector spaces over the same
field, we say a family $\mathcal{F}$ of linear maps from $V$ to $W$ is
\emph{$(t-1)$-intersection-free} if for any two linear maps $\sigma_1,\sigma_2
\in \mathcal{F}$, $\dim(\{v \in V:\ \sigma_1(v)=\sigma_2(v)\}) \neq t-1$. We
prove that if $n$ is sufficiently large depending on $t$, $q$ is any prime
power, $V$ is an $n$-dimensional vector space over $\mathbb{F}_q$, and
$\mathcal{F} \subset \textrm{GL}(V)$ is $(t-1)$-intersection-free, then
$|\mathcal{F}| \leq \prod_{i=1}^{n-t}(q^n - q^{i+t-1})$. Equality holds only if
there exists a $t$-dimensional subspace of $V$ on which all elements of
$\mathcal{F}$ agree, or a $t$-dimensional subspace of $V^*$ on which all
elements of $\{\sigma^*:\ \sigma \in \mathcal{F}\}$ agree. Our main tool is a
`junta approximation' result for families of linear maps with a forbidden
intersection: namely, that if $V$ and $W$ are finite-dimensional vector spaces
over the same finite field, then any $(t-1)$-intersection-free family of linear
maps from $V$ to $W$ is essentially contained in a $t$-intersecting
\emph{junta} (meaning, a family $\mathcal{J}$ of linear maps from $V$ to $W$
such that the membership of $\sigma$ in $\mathcal{J}$ is determined by
$\sigma(v_1),\ldots,\sigma(v_M),\sigma^*(a_1),\ldots,\sigma^*(a_N)$, where
$v_1,\ldots,v_M \in V$, $a_1,\ldots,a_N \in W^*$ and $M+N$ is bounded). The
proof of this in turn relies on a variant of the `junta method' (originally
introduced by Dinur and Friedgut, and powefully extended by Keller and the last
author), together with spectral techniques and a hypercontractive inequality.
