We compute the two-loop fermion self-energy in massless reduced quantum electrodynamics (RQED) for an arbitrary gauge in the case where the photon field is three-dimensional and the fermion field two-dimensional: super-renormalizable RQED3,2 with NF fermions. We find that the theory is infrared finite at two-loop and that finite corrections to the fermion propagator have a remarkably simple form.One of the building blocks of multi-loop calculations is the two-loop massless propagator diagram, see Fig. 1:where G is the so-called coefficient function of the diagram, α i are arbitrary indices and p is an external momentum in a Minkowski space-time of dimensionality d e . This diagram is at the heart of numerous radiative correction calculations in quantum field theory and associated to the development of sophisticated methods such as, e.g., the Gegenbauer polynomial technique 1,2 , integration by parts 3,4 , and the method of uniqueness 3,5,6 , see Ref.[8] for a historical review on this diagram. In the case where all indices are integers, this diagram is well known and can be expressed in terms of recursively one-loop diagrams. When all indices are arbitrary, the result is highly non-trivial and can be represented 9 as a combination of two-fold series. In some intermediate cases, simpler forms can be obtained. 2,3,7,[10][11][12]14 In particular, in Ref.[2], an ingenious transformation was found from Gegenbauer two-fold series to one-fold 3 F 2 -hypergeometric series of unit argument for a complicated class of diagrams having two integer indices on adjacent lines and three other arbitrary indices. For this class of diagrams, similar results have been found in Ref. [11] using an ansatz to solve the recurrence relations arising from integration by parts. In Ref.[2], the results were applied to the computation of a diagram with a single non-integer index on the central line. This important diagram appears in various calculations, see, e.g., Refs. [3,7,10,13,14]; it was shown in Ref.[2] to reduce to a single 3 F 2 -hypergeometric series of unit argument. More recently, in Ref. [15], the results of [2] were applied to the case involving two arbitrary indices on non adjacent lines. In this case, the corresponding coefficient function: was shown to reduce to two 3 F 2 -hypergeometric series of argument 1. In Ref.[15], Eq. (2) appeared in the computation of the two-loop fermion self-energy in reduced quantum electrodynamics (RQED), [16], or RQED dγ ,de , see also Refs. [17] in relation with RQED 4,3 . In the general case, this relativistic model describes the interaction of an abelian U (1) gauge field living in d γ space-time dimensions with a fermion field localized in a reduced space-time of d e dimensions (d e d γ ). In RQED dγ ,de , while the bubble and rainbow diagrams, Figs. 2 a) and 2 b), respectively, naturally reduce to recursively one-loop diagrams, the crossed photon diagram, Fig. 2 c), involves a contribution of the type Eq. (2) with the indices given by:where, following the notation of Ref.[15], d γ = 4 − 2ε ...