Ultra-lightweight characteristics while maintaining reasonably high specific strength are always demanding features in structural applications. In this regard, porous structures become advantageous because of their porous architectures--especially when the pores are fluid-filled, which contributes to additional stiffness and time-dependent responses. However, these porous architectures inherently exhibit randomness in their geometry, which is difficult to control precisely. From another perspective, due to real-world manufacturing constraints, every structure contains some degree of porosity, introducing uncertainty in predicting its mechanical behaviour [1]. In the present paper, the manner in which uncertainty is induced in fluid-filled porous structures and its quantification through a simplified perturbation theory are discussed. In other words, how randomness in the porous architecture affects the overall stiffness of the structure is analysed analytically. Such probabilistic analytical characterization not only builds an alternate solution to highly computationally intensive probabilistic methods like Monte-Carlo simulations [2], but also forms a foundation for the design, analysis, and reliability assessment of advanced lightweight systems and components that operate under highly uncertain conditions such as aircraft wings, fuselages, rocket components, satellite frames and so on. REFERENCES [1] Al-Maharma, Ahmad Y, Patil, Sandeep P and Markert, Bernd. “Effects of porosity on the mechanical properties of additively manufactured components: a critical review.” Materials Research Express Vol. 7 No. 12 (2020): p. 122001. [2] Feng, YT, Li, CF and Owen, DRJ2608034. “A directed Monte Carlo solution of linear stochastic algebraic system of equations.” Finite Elements in Analysis and Design Vol. 46 No. 6 (2010): pp. 462–473.