In cyclic universe models based on a single scalar field (e.g., the radion determining the distance between branes in M-theory), virtually the entire universe makes it through the ekpyrotic smoothing and flattening phase, bounces, and enters a new epoch of expansion and cooling. This stable evolution cannot occur, however, if scale-invariant curvature perturbations are produced by the entropic mechanism because it requires two scalar fields (e.g., the radion and the Calabi-Yau dilaton) evolving along an unstable classical trajectory. In fact, we show here that an overwhelming fraction of the universe fails to make it through the ekpyrotic phase; nevertheless, a sufficient volume survives and cycling continues forever provided the dark energy phase of the cycle lasts long enough, of order a trillion years. Two consequences are a new role for dark energy and a global structure of the universe radically different from that of eternal inflation.Lemaitre [1] invoked the mythical "phoenix" to refer to an oscillatory cosmology in which the universe undergoes regular periods of expansion and contraction with a big crunch/big bang transition in between. His model was a closed universe in which the reversal from expansion to contraction is caused by an overdensity of matter and radiation. Although this model is ruled out by WMAP measurements [2] indicating a flat universe, there remains the more recent proposal of a cyclic model of the universe [3, 4] (see [5] for a recent review) that also undergoes regular cycles of evolution beginning with a big bang and ending in a big crunch. Unlike Lemaitre's model, the cyclic universe is kept smooth and spatially flat by a period of ekpyrotic contraction [6,7] (slow contraction with equation of state w ≫ 1) that precedes each big crunch. The expansion, contraction and smoothing are governed by a scalar field φ 1 that evolves along a potential V (φ 1 ). In a version inspired by M theory [8], the cycles correspond to the regular collision and rebound of two orbifold planes, and φ 1 is the modulus field whose value determines the distance between orbifold planes. As in Lemaitre's oscillatory model, the notion is that virtually the entire universe makes it through the big crunch/big bang transition and continues into the next cycle.In this paper, we show how the generation of scaleinvariant density perturbations may lead to a variation of the cyclic model that may be more fittingly called a "phoenix universe," in the sense that most of the universe is turned to "ash" at the end of each cycle and the universe is reborn from a comparatively tiny surviving seed. The phoenix effect is an unintended byproduct of generating curvature perturbations via the entropic mechanism [9]. The entropic mechanism was introduced because an ekpyrotic contraction phase with only a single scalar field produces scale-invariant time-delay perturbations, but not scale-invariant curvature perturbations [10]. Although there are various proposals for circumventing this problem [9,11], the entropic mechanism is cu...