D614G is a missense mutation that affects the spike protein of SARS-CoV-2. The frequency of this mutation in the viral population has increased during the pandemic. G (glycine) has replaced D (aspartic acid) at position 614 in many countries, especially in Europe though more slowly in China and the rest of East Asia, supporting the hypothesis that G increases the transmission rate, which is consistent with higher viral titers and infectivity in vitro.

In July 2020, it was reported that the more infectious D614G SARS-CoV-2 variant had become the dominant form in the pandemic. PHE confirmed that the D614G mutation had a "moderate effect on transmissibility" and was being tracked internationally.

The global prevalence of D614G correlates with the prevalence of loss of smell (anosmia) as a symptom of COVID-19, possibly mediated by higher binding of the RBD to the ACE2 receptor or higher protein stability and hence higher infectivity of the olfactory epithelium.
Variants containing the D614G mutation are found in the G clade by GISAID and the B.1 clade by the PANGOLIN tool.