Can a good person go to heaven without being a Christian?

Christians genuinely disagree, so it's worth naming the real positions rather than picking one and calling it "the" Christian answer.

Exclusivism, historically the majority view across most Christian traditions, holds that explicit faith in Christ is necessary for salvation. It points to Jesus' claim to be "the way, the truth, and the life" and the apostles' preaching that salvation exists "in no one else."

Inclusivism holds that Christ's death remains the only actual basis for salvation, but that its benefits might reach people who never heard the gospel yet responded in faith to whatever knowledge of God they had. This has real support in Catholic teaching since Vatican II, which affirms that those who, through no fault of their own, don't know the gospel but sincerely seek God and follow conscience may attain salvation.

Both reject the separate idea that any sincere religion works equally—inclusivism still holds Christ's atonement as the sole basis, just possibly applied more broadly than exclusivism allows.