We introduce a new avatar of a Frobenius P-category F under the form of a suitable subring HF of the double Burnside ring of P -- called the Hecke algebra of F- where we are able to formulate: (i) the generalization to a Frobenius P-category of the Alperin Fusion Theorem, (ii) the "canonical decomposition" of the morphisms in the exterior quotient of a Frobenius P-category restricted to the selfcentralizing objects as developed in chapter 6 of [4], and (iii) the "basic P * P-sets" in chapter 21 of [4] with its generalization by Kari Ragnarsson and Radu Stancu to the virtual P *P-sets in [6]. We also explain the relationship with the usual Hecke algebra of a finite group.