Many African nations want France out. This country wants it in.

KIGALI, Rwanda — After decades of wielding political, military and economic power across Africa, France is scaling back its presence on the continent as it faces significant resentment in many African countries. Yet one nation has emerged as an exception: Rwanda.

As other African nations seek to reduce France's influence, Rwanda is embracing it, celebrating French culture, language and food, despite decades of frosty relations with Paris over its role in the 1994 Rwanda genocide. In return, French companies are scaling up their investments in Rwanda.

The détente, which is being championed by Rwanda's longtime leader, Paul Kagame, has garnered France a much-needed security partner in Africa and secured Rwanda millions of dollars in development and trade funds. The warming relations are also rare good news for French President Emmanuel Macron, who has...