When Pope Francis apologizes to Indigenous groups on Canadian soil this week, he will make another effort toward healing harms inflicted at church-run residential schools — and add to the Catholic Church's growing ledger of atonement for past transgressions.

Like the papacy, top Protestant leaders also have gradually issued institutional mea culpas for their churches' historical wrongs. Many of the apologies on behalf of Christian denominations are for grave offenses: genocide, sex abuse, slavery, war and more.

While increasingly common, the ecclesial apology is a relatively modern phenomenon,...