The web of dual gauge theories engineered from a class of toric Calabi-Yau threefolds is explored. In previous work, we have argued for a triality structure by compiling evidence for the fact that every such manifold X N,M (for given (N, M )) engineers three a priori different, weakly coupled quiver gauge theories in five dimensions. The strong coupling regime of the latter is in general described by Little String Theories. Furthermore, we also conjectured that the manifold X N,M is dual to X N ,M if N M = N M and gcd(N, M ) = gcd(N , M ). Combining this result with the triality structure, we currently argue for a large number of dual quiver gauge theories, whose instanton partition functions can be computed explicitly as specific expansions of the topological partition function Z N,M of X N,M . We illustrate this web of dual theories by studying explicit examples in detail. We also undertake first steps in further analysing the extended moduli space of X N,M with the goal of finding other dual gauge theories. the given conditions, the Kähler cones of the Calabi-Yau manifolds X N,M and X N ,M are part of a common extended moduli space. The relation (1.1) was explicitly shown for a large class of examples and passed highly non-trivial consistency checks for generic (N, M ). Moreover, it is expected that the partition functions Z N,M and Z N ,M agree upon taking into account the duality map implicit in (1.1). This fact was explicitly checked for gcd(N, M ) = 1 in [30].Secondly, in [32] the question was analysed what type of (low-energy) gauge theories can be engineered from a given Calabi-Yau manifold X N,M . By studying different series expansions of Z N,M (in terms of different sets of the Kähler parameters of X N,M ) it was found that the Kähler cone of X N,M contains three different regions that engineer five-dimensional quiver gauge theories with gauge groups( 1.2) respectively, where k = gcd(N, M ). It is expected that the UV completions of (at least some of) these gauge theories are LSTs. The relation among the three low-energy theories with gauge groups (1.2) was dubbed triality in [32], reflecting the fact that all three are engineered by the same Calabi-Yau threefold. It is important to realise that the mapping of the various gauge theory parameters is highly non-trivial among the members of the triality: indeed, the coupling constants, mass parameters and other Coulomb branch parameters are mixed in a highly non-trivial fashion when going from one theory to another.Combining the triality discussed in [32] with the observations of [31] that the Calabi-Yau manifold X N,M itself can be dualised to other manifolds in the sense of eq. (1.1) suggests an even more elaborate picture at the level of the low-energy theories: indeed it implies that a (circular) quiver gauge theory with N gauge nodes of type U (M ) (that is engineered by X N,M for arbitrary (N, M )) is dual to a whole web of other quiver gauge theories that have N gauge nodes of type U (M ) such that N M = N M and gcd(N, M ) = gcd(N , M ). In this p...