The mitochondrial haplogroup T, characterized by the nucleotide motif 16126C-16294T in the hypervariable segment I (HVS I), is one of the most frequent among Europeans.

This haplogroup includes the only well-resolved subgroup, T1, but that other HVS I sequences cannot be differentiated into subgroups due to possible homoplasies at nucleotide positions 16292, 16296 and 16304, leading to the reticulations in the topology of phylogenetic networks.