Plettenberg (German: [ˈplɛtn̩ˌbɛʁk] ⓘ; Westphalian: Plettmert) is a town in the Märkischer Kreis, in North Rhine-Westphalia, Germany.

The Dukes of the Mark bought the town from Cologne, who in 1301 built the castle Schwarzenberg (which was destroyed by fire in 1864).

The coat of arms of the municipality of Plettenberg-Land showed a silver-blue shield split vertically, the symbol of the master of Plettenberg.

The coat of arms of the Amt Plettenberg was very similar, it only had an additional red shell in the top-left-hand corner as the symbol of the masters of Ohle.

The coat of arms of the municipality of Ohle shows the Saint Martin of Tours splitting his cloak to share with the beggar.

A small escutcheon is placed next to the Saint, showing a red shell on a yellow background, the symbol of the masters of Ohle.