  The Forward Calorimeter (FoCal) is a new sub-detector in ALICE to be
installed during the LHC Long Shutdown 3 for LHC Run 4. It consists of a
highly-granular Si+W electromagnetic calorimeter combined with a conventional
metal-scintillator hadronic calorimeter, covering a pseudorapidity interval of
$3.2<\eta<5.8$. The FoCal is optimised to measure various physics quantities in
the forward region, allowing exploration of the gluon density in hadronic
matter down to $x\sim10^{-6}$, thus providing insights into non-linear QCD
evolution at the LHC. These proceedings introduce the FoCal physics program and
its corresponding performance. Additionally, the performance of the FoCal
prototype will be presented.
