The 2020 event that helped plunge global stock markets as oil producers failed to agree on production cuts was the 2020 Russia–Saudi Arabia oil-price war.
On March 6, 2020, Russia and OPEC failed to reach an agreement on additional production cuts. Saudi Arabia then announced major price reductions and plans to increase output, while demand was already weakening as the COVID-19 pandemic spread.
Oil prices collapsed, energy shares fell, and investors faced a shock combining a commodity-price war with rapidly worsening public-health and economic news. Global equity markets suffered severe losses during March 2020.
The episode is distinct from the later pandemic crash itself, though the two shocks overlapped. The oil dispute was resolved after major producers agreed to historic production reductions in April 2020.