We introduce a model of interacting Majorana fermions that describes a superconducting phase with a topological order characterized by the Fibonacci topological field theory. Our theory, which is based on a SO(7)1/(G2)1 coset factorization, leads to a solvable one dimensional model that is extended to two dimensions using a network construction. In addition to providing a description of the Fibonacci phase without parafermions, our theory predicts a closely related "anti-Fibonacci" phase, whose topological order is characterized by the tricritical Ising model. We show that Majorana fermions can split into a pair of Fibonacci anyons, and propose an interferometer that generalizes the Z2 Majorana interferometer and directly probes the Fibonacci non-Abelian statistics.Current interest in topological quantum phases is heightened by the proposal to use them for quantum information processing [1,2] and by prospects for realizing them in experimentally viable electronic systems. There is growing evidence that the fractional quantum Hall (QH) state at filling ν = 5/2 is a non-Abelian state [3][4][5][6][7] with Ising topological order. A simpler form of Ising order is predicted in topological superconductors (T-SC) [8,9] and in SC proximity effect devices [10][11][12][13][14]. In these systems the Ising σ particle is not dynamical, but is associated with domain walls or vortices that host gapless Majorana fermion modes. Recent experiments have found promising evidence for Majorana fermions in 1D and 2D SC systems [15][16][17].Ising topological order is insufficient for universal quantum computation, but the richer Fibonacci topological order is sufficient [18]. Fibonacci order arises in the Z 3 parafermion state introduced by Read and Rezayi[19], which is a candidate for the fractional QH state at ν = 12/5. Parafermions can also be realized by combining SC with the fractional QH effect [20][21][22][23][24]. This line of inquiry culminated in the tour de force works [25,26] that showed a ν = 2/3 QH state, appropriately proximitized, could exhibit a Fibonacci phase.In this paper we introduce a different formulation of the Fibonacci phase based on a model of interacting Majorana fermions. Our starting point is a system of chiral Majorana edge states, which can in principle be realized in SC proximity effect structures. We show that a particular four fermion interaction leads to an essentially exactly solvable model that realizes the Fibonacci phase. In addition to providing a direct route to the Fibonacci phase without parafermions, our theory reveals a distinct but closely related "anti-Fibonacci" state that is a kind of particle-hole conjugate to the Fibonacci state with a topological order that combines Ising and Fibonacci. Our formulation also suggests a method for experimentally probing the Fibonacci state. We introduce a generalization of the interferometer introduced earlier for Majorana states [27,28], and argue that it provides a method for unambiguously detecting Fibonacci order.The fact that interacting Majorana ...