  We show that gauge coupling unification in SUSY models can make a non-trivial
interconnection between collider and proton decay experiments. Under the
assumption of precise gauge coupling unification in the MSSM, the low energy
SUSY spectrum and the unification scale are intertwined, and the lower bound on
the proton lifetime can be translated into upper bounds on SUSY masses. We
found that the current limit on $\tau(p \to \pi^0 e^+)$ already excludes
gluinos and winos heavier than $\sim 120$ and 40 TeV, respectively, if their
mass ratio is $M_3/M_2 \sim 3$. Next generation nucleon decay experiments are
expected to bring these upper bounds down to $\sim 10$ and 3 TeV.
