The Telomere-to-Telomere (T2T) Consortium has completed a full sequence of a human genome, T2T-CHM13, which includes 3.055 billion base pairs and covers all 22 autosomes and Chromosome X. This sequence addresses the 8% of the genome that was previously unfinished, primarily centromeric regions and short arms of acrocentric chromosomes. The T2T-CHM13 assembly is gapless and corrects errors in the previous reference genome, GRCh38, which contains 151 million base pairs of unknown sequence. The T2T-CHM13 assembly is more complete and accurate, reducing both false-negative and false-positive variant calls, and is a more representative reference for variant calling across human samples. The T2T-CHM13 assembly also uncovers the genomic structure of the short arms of the five acrocentric chromosomes, which have been largely unsequenced due to their complex composition of satellite repeats and segmental duplications. The T2T-CHM13 assembly provides a more comprehensive and accurate reference for future studies of human genomic variation and disease.The Telomere-to-Telomere (T2T) Consortium has completed a full sequence of a human genome, T2T-CHM13, which includes 3.055 billion base pairs and covers all 22 autosomes and Chromosome X. This sequence addresses the 8% of the genome that was previously unfinished, primarily centromeric regions and short arms of acrocentric chromosomes. The T2T-CHM13 assembly is gapless and corrects errors in the previous reference genome, GRCh38, which contains 151 million base pairs of unknown sequence. The T2T-CHM13 assembly is more complete and accurate, reducing both false-negative and false-positive variant calls, and is a more representative reference for variant calling across human samples. The T2T-CHM13 assembly also uncovers the genomic structure of the short arms of the five acrocentric chromosomes, which have been largely unsequenced due to their complex composition of satellite repeats and segmental duplications. The T2T-CHM13 assembly provides a more comprehensive and accurate reference for future studies of human genomic variation and disease.