This dataset comprises human T cell transcriptomic data from the GEO series on infant and adult T cells across tissues, with this sample representing unstimulated spleen-derived T cells from a 0.75-year-old female donor. It contains single-cell RNA-seq profiles generated from negatively selected pan T cells using the 10x Genomics Chromium platform and Illumina NovaSeq 6000 sequencing, with processed gene expression count matrices aligned to GRCh38. The data support analysis of T cell states, diversity, and tissue-specific immune characteristics across human development and anatomical sites.