Aims and Objectives/Purpose/Research Questions: This Introduction outlines the aims, scope, and structure of the Special Issue. The volume examines (1) the continuing role of Russian in former Soviet republics and its effects on regional varieties of Russian and autochthonous languages; (2) the transgenerational trajectories of autochthonous languages in homeland and diasporic settings; and (3) the functions of Russian as a lingua franca in migration contexts and its influence on other post-Soviet languages. Design/Methodology/Approach: The Introduction is designed as an overview of the topic under scrutiny, situating the Special Issue within broader research scholarly and geopolitical contexts. Findings/Conclusions: The contributions to this Special Issue address diverse manifestations of multilingualism in the post-Soviet space and its diasporas, highlighting processes of language maintenance, shift, contact-induced change, and linguistic convergence. They also point to further research on intergenerational language transmission, triadic language contact, and the evolution of Russian-based transferred bilingualism in the context of contemporary geopolitical transformations. By situating post-Soviet language practices within global debates on bilingualism and language contact, the volume contributes to a more nuanced understanding of convergence and diversity in post-imperial multilingual spaces. Originality: The Special Issue conceptualizes the post-Soviet diaspora as a transnational contact zone shaped by overlapping imperial, national, and migratory language regimes. It brings together studies of Russian and autochthonous languages across both homeland and diasporic contexts, illuminating patterns of linguistic convergence and diversity. Significance/Implications: Drawing on contact linguistics, sociolinguistics, linguistic typology, and postcolonial perspectives, the volume advances the study of post-imperial versus postcolonial multilingualism and contributes to broader theories of language change, evolution, and diversity in multilingual settings.