Merge conflicts in GitHub pull requests occur when changes in your branch overlap with changes in the base branch, especially if both modified the same lines. To resolve conflicts, pull the latest changes from the base branch (e.g., `main`) into your feature branch with `git pull origin main`. Git will flag conflicting files, showing both versions. Open each conflicted file, where you’ll see markers indicating the base branch’s and your branch’s versions. Decide which changes to keep, edit as needed, then remove conflict markers before saving. Once resolved, mark conflicts as resolved with `git add ` for each file, and commit with `git commit`. Push the resolved changes to GitHub; the conflict should now be cleared, allowing the pull request to merge smoothly. Always test your code after conflict resolution to ensure the combined changes work as expected.