A quantum phase transition is usually achieved by tuning physical parameters in a Hamiltonian at zero temperature. Here, we show that the ground state of a topological phase itself encodes critical properties of its transition to a trivial phase. To extract this information, we introduce an extensive partition of the system into two subsystems both of which extend throughout the bulk in all directions. The resulting bulk entanglement spectrum has a low-lying part that resembles the excitation spectrum of a bulk Hamiltonian, which allows us to probe a topological phase transition from a single wave function by tuning either the geometry of the partition or the entanglement temperature. As an example, this remarkable correspondence between the topological phase transition and the entanglement criticality is rigorously established for integer quantum Hall states. DOI: 10.1103/PhysRevLett.113.106801 PACS numbers: 73.43.Cd, 03.67.Mn Topological phases of matter are characterized by quantized physical properties that arise from topological quantum numbers. For instance, the quantized Hall conductance of an integer quantum Hall state is determined by its Chern number [1], the quantized magnetoelectric response of a topological insulator is governed by its Z 2 topological invariant [2][3][4], and the quasiparticle charge in a fractional quantum Hall state is deeply related to its topological degeneracy [5]. Remarkably, the complete set of topological quantum numbers, or topological order [6], is entirely encoded in the ground state wave function, which can be computed either directly [1,7] or from the topological entanglement entropy [8][9][10][11][12][13].To extract more information about a topological phase from its ground state wave function, Li and Haldane [14] considered the full entanglement spectrum of the reduced density matrix upon tracing out a subsystem. When a topologically nontrivial ground state is spatially divided into two halves, the resulting entanglement spectrum bears a remarkable similarity to the edge state spectrum of the system in the presence of a physical boundary [16][17][18][19][20][21][22]. Given this capability of the entanglement spectrum to simulate edge excitations, one may wonder if universal bulk properties of topological phases can also be obtained via entanglement.In this work, we show that the ground state of a topological phase (a single wave function) encodes information on its phase transition to a trivial product state, despite the fact that the system itself is away from the phase transition. To expose this "hidden" topological phase transition, we introduce a new type of real-space partitions, which divide the system into two parts that are extensive with system size in all directions, as shown in Fig. 1. The entanglement Hamiltonian obtained from such an extensive partition is a bulk entity, which we term the bulk entanglement Hamiltonian. The corresponding bulk entanglement spectrum (BES) has a low-lying part that resembles the excitation spectrum of a physical system in...