  The trilinear Higgs coupling $\lambda_{hhh}$ is crucial for determining the
structure of the Higgs potential and for probing possible effects of physics
beyond the Standard Model (SM). Focusing on the Two-Higgs-Doublet Model as a
concrete example, we identify parameter regions in which $\lambda_{hhh}$ is
significantly enhanced with respect to the SM. Taking into account all relevant
corrections up to the two-loop level, we show that already current experimental
bounds on $\lambda_{hhh}$ rule out significant parts of the parameter space
that would otherwise be unconstrained. We illustrate the interpretation of the
results on $\lambda_{hhh}$ for a benchmark scenario. Similar results are
expected for wide classes of models with extended Higgs sectors.
