<p>The pig serves as both an important agricultural species and a valuable biomedical model due to its physiological and immunological similarities to humans. RNA editing, especially adenosine-to-inosine (A-to-I) conversions, is a key post-transcriptional mechanism that regulates gene expression and immune responses. However, the dynamics of RNA editing during porcine spleen development are still underexplored. To address this, we systematically profiled the RNA editing landscape of Ningxiang pig spleens at three developmental stages (30, 90, and 210 days) to investigate the dynamic regulation of RNA editing during immune system maturation. A total of 72,182 high-confidence RNA editing sites were identified, of which 92.9% corresponded to A-to-I conversions. These sites were predominantly located within swine-specific SINE retrotransposons (PRE-1/Pre0_SS). Across developmental stages, 2,649 sites exhibited significant differential editing, indicating that RNA editing activity is dynami-cally regulated during spleen development. Functional enrichment analysis of the differentially edited genes revealed enrichment in immune-related pathways, particularly those involved in T cell activation, cytokine signaling, and antiviral defense. Protein–protein interaction analysis further revealed two key RNA-editing–associated modules centered on PTPN11 and EP300, underscoring regulatory of immune signaling and disease response. Collectively, these results demonstrate that RNA editing constitutes a dynamic and developmentally regulated post-transcriptional layer during spleen development. Our findings highlight RNA editing as an important regulatory mechanism contributing to immune maturation and provide a valuable resource for future studies on immune regulation and disease resistance in pigs.</p>