Joachim Zachris Duncker (12 November 1774 – 6 July 1809) was a Swedish soldier born in Ristiina in Savonia.

During the Battle of Pulkkila (2 May 1808) he distinguished himself so well that Johan August Sandels gave him the honorary assignment to bring the news of the victory to the Swedish king.

During the Battle of Koljonvirta (27 October 1808), Duncker together with Colonel Fahlander and Major Malm and only 600 men helped Sandels to utterly defeated a superior Russian force.

During the Battle of Hörnefors (5 July 1809) Duncker commanded the Swedish rearguard and received fatal wounds and died in the Russian encampment the day after.

Duncker was buried next to Umeå church by the Russians that gave him a full honour guard.