Recent technological advances have facilitated the assembly of telomere-to-telomere (T2T) genomes. The current T2T CHM13 showcases the complete architecture of the human genome, yet its use in functional experiments is limited by discrepancies with the actual genome of the specific biological system under study. Access to reference assemblies for experimentally relevant cell lines is therefore essential in advancing sequencing-based analyses and precise manipulation, particularly in highly variable regions such as centromeres. Here, we present RPE1v1.1, the near-complete diploid genome assembly of the hTERT RPE-1 cell line, a non-cancerous human retinal epithelial model with a stable karyotype. Using high-coverage Pacific Biosciences and Oxford Nanopore Technologies long-read sequencing, we generate a high-quality de novo assembly, validate it through multiple methods, and phase it by integrating high-throughput chromosome conformation capture (Hi-C) data. Our assembly includes chromosome-level scaffolds that span centromeres for all chromosomes. Comparing both haplotypes with the CHM13 genome, we detect haplotype-specific genomic variations, including the translocation between chromosome 10 and chromosome X t(X;10)(Xq28;10q21.2) characteristic of RPE-1 cells, and divergence peaking at centromeres. Altogether, the RPE1v1.1 genome provides a reference-quality diploid assembly of a widely used cell line, supporting high-precision genetic and epigenetic studies in this model system.