This paper explores the size size–dependent vibration response of porous functionally graded (FG) micro/nanobeams based on an integrated nonlocal nonlocal-couple stress continuum model (NLCS) NLCS). The mutual effect of the microstructure local rotation and nonlocality are modelled using the modified couple stress theory and Eringen nonlocal elasticity theory theory, respectivelyrespectively, into the classical E uleruler–Bernoulli beam model model. All the material properties of the bulk continuum including the microstructure material length scale parameter (MLSP) are assumed to be graded along the thickness according to a power law law. For the first timetime, the effect of the po rosity and voids on the modulus of elasticity and MLSP is taken as a ratio of the mass density with porosityporosity-to -that without porosity porosity. Accounting for the physical neutral axis concept and generalized elasticity theory theory, Hamilton's principle is utilized to f ormulate the equations of motion and boundary conditions for the FG porous micro/nanobeams nanobeams. The analytical solution using Navier method is applied to solve the governing equations and obtain the results results. The impact of different parameters such as the grada tion index index, porosity pattern pattern, porosity parameter parameter, nonlocal parameter parameter, and MLSP on the free vibration characteristics of simply supported FG nanobeams are presented discussed in detail detail. The current model is efficient in many applications used porous FGM FGM, su ch as aerospace aerospace, nuclearnuclear, power plane sheller sheller, and marine structures structures.