diff --git a/src/pip/_internal/resolution/resolvelib/reporter.py b/src/pip/_internal/resolution/resolvelib/reporter.py
index 65c437373..07ce399ac 100644
--- a/src/pip/_internal/resolution/resolvelib/reporter.py
+++ b/src/pip/_internal/resolution/resolvelib/reporter.py
@@ -6,9 +6,9 @@ from pip._vendor.resolvelib.reporters import BaseReporter
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 
 if MYPY_CHECK_RUNNING:
-    from typing import DefaultDict
+    from typing import Any, DefaultDict
 
-    from .base import Candidate
+    from .base import Candidate, Requirement
 
 
 logger = getLogger(__name__)
@@ -50,3 +50,35 @@ class PipReporter(BaseReporter):
 
         message = self._messages_at_backtrack[count]
         logger.info("INFO: %s", message)
+
+
+class PipDebuggingReporter(BaseReporter):
+    """A reporter that does an info log for every event it sees."""
+
+    def starting(self):
+        # type: () -> None
+        logger.info("Reporter.starting()")
+
+    def starting_round(self, index):
+        # type: (int) -> None
+        logger.info("Reporter.starting_round(%r)", index)
+
+    def ending_round(self, index, state):
+        # type: (int, Any) -> None
+        logger.info("Reporter.ending_round(%r, state)", index)
+
+    def ending(self, state):
+        # type: (Any) -> None
+        logger.info("Reporter.ending(%r)", state)
+
+    def adding_requirement(self, requirement, parent):
+        # type: (Requirement, Candidate) -> None
+        logger.info("Reporter.adding_requirement(%r, %r)", requirement, parent)
+
+    def backtracking(self, candidate):
+        # type: (Candidate) -> None
+        logger.info("Reporter.backtracking(%r)", candidate)
+
+    def pinning(self, candidate):
+        # type: (Candidate) -> None
+        logger.info("Reporter.pinning(%r)", candidate)
diff --git a/src/pip/_internal/resolution/resolvelib/resolver.py b/src/pip/_internal/resolution/resolvelib/resolver.py
index 65d087412..e2e164d12 100644
--- a/src/pip/_internal/resolution/resolvelib/resolver.py
+++ b/src/pip/_internal/resolution/resolvelib/resolver.py
@@ -1,5 +1,6 @@
 import functools
 import logging
+import os
 
 from pip._vendor import six
 from pip._vendor.packaging.utils import canonicalize_name
@@ -11,7 +12,10 @@ from pip._internal.req.req_install import check_invalid_constraint_type
 from pip._internal.req.req_set import RequirementSet
 from pip._internal.resolution.base import BaseResolver
 from pip._internal.resolution.resolvelib.provider import PipProvider
-from pip._internal.resolution.resolvelib.reporter import PipReporter
+from pip._internal.resolution.resolvelib.reporter import (
+    PipDebuggingReporter,
+    PipReporter,
+)
 from pip._internal.utils.misc import dist_is_editable
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 
@@ -104,7 +108,10 @@ class Resolver(BaseResolver):
             upgrade_strategy=self.upgrade_strategy,
             user_requested=user_requested,
         )
-        reporter = PipReporter()
+        if "PIP_RESOLVER_DEBUG" in os.environ:
+            reporter = PipDebuggingReporter()
+        else:
+            reporter = PipReporter()
         resolver = RLResolver(provider, reporter)
 
         try: