  A typical decomposition question asks whether the edges of some graph $G$ can
be partitioned into disjoint copies of another graph $H$. One of the oldest and
best known conjectures in this area, posed by Ringel in 1963, concerns the
decomposition of complete graphs into edge-disjoint copies of a tree. It says
that any tree with $n$ edges packs $2n+1$ times into the complete graph
$K_{2n+1}$. In this paper, we prove this conjecture for large $n$.
