diff --git a/src/pytorch_lightning/loggers/tensorboard.py b/src/pytorch_lightning/loggers/tensorboard.py
index f61959a5dd60d..50d6e95add25b 100644
--- a/src/pytorch_lightning/loggers/tensorboard.py
+++ b/src/pytorch_lightning/loggers/tensorboard.py
@@ -28,6 +28,7 @@
 
 import pytorch_lightning as pl
 from lightning_lite.utilities.cloud_io import get_filesystem
+from lightning_lite.utilities.types import _PATH
 from pytorch_lightning.core.saving import save_hparams_to_yaml
 from pytorch_lightning.loggers.logger import Logger, rank_zero_experiment
 from pytorch_lightning.utilities.imports import _OMEGACONF_AVAILABLE
@@ -87,20 +88,21 @@ class TensorBoardLogger(Logger):
 
     def __init__(
         self,
-        save_dir: str,
+        save_dir: _PATH,
         name: Optional[str] = "lightning_logs",
         version: Optional[Union[int, str]] = None,
         log_graph: bool = False,
         default_hp_metric: bool = True,
         prefix: str = "",
-        sub_dir: Optional[str] = None,
+        sub_dir: Optional[_PATH] = None,
         **kwargs: Any,
     ):
         super().__init__()
+        save_dir = os.fspath(save_dir)
         self._save_dir = save_dir
         self._name = name or ""
         self._version = version
-        self._sub_dir = sub_dir
+        self._sub_dir = None if sub_dir is None else os.fspath(sub_dir)
         self._log_graph = log_graph
         self._default_hp_metric = default_hp_metric
         self._prefix = prefix
diff --git a/src/pytorch_lightning/loggers/wandb.py b/src/pytorch_lightning/loggers/wandb.py
index 55757487d7124..c61052762f868 100644
--- a/src/pytorch_lightning/loggers/wandb.py
+++ b/src/pytorch_lightning/loggers/wandb.py
@@ -24,6 +24,7 @@
 from lightning_utilities.core.imports import RequirementCache
 from torch import Tensor
 
+from lightning_lite.utilities.types import _PATH
 from pytorch_lightning.callbacks import Checkpoint
 from pytorch_lightning.loggers.logger import Logger, rank_zero_experiment
 from pytorch_lightning.utilities.exceptions import MisconfigurationException
@@ -292,10 +293,10 @@ def any_lightning_module_function_or_hook(self):
     def __init__(
         self,
         name: Optional[str] = None,
-        save_dir: str = ".",
+        save_dir: _PATH = ".",
         version: Optional[str] = None,
         offline: bool = False,
-        dir: Optional[str] = None,
+        dir: Optional[_PATH] = None,
         id: Optional[str] = None,
         anonymous: Optional[bool] = None,
         project: str = "lightning_logs",
@@ -331,6 +332,13 @@ def __init__(
         self._experiment = experiment
         self._logged_model_time: Dict[str, float] = {}
         self._checkpoint_callback: Optional[Checkpoint] = None
+
+        # paths are processed as strings
+        if save_dir is not None:
+            save_dir = os.fspath(save_dir)
+        elif dir is not None:
+            dir = os.fspath(dir)
+
         # set wandb init arguments
         self._wandb_init: Dict[str, Any] = dict(
             name=name,
@@ -521,7 +529,7 @@ def after_save_checkpoint(self, checkpoint_callback: Checkpoint) -> None:
     @rank_zero_only
     def download_artifact(
         artifact: str,
-        save_dir: Optional[str] = None,
+        save_dir: Optional[_PATH] = None,
         artifact_type: Optional[str] = None,
         use_artifact: Optional[bool] = True,
     ) -> str:
@@ -542,6 +550,7 @@ def download_artifact(
             api = wandb.Api()
             artifact = api.artifact(artifact, type=artifact_type)
 
+        save_dir = None if save_dir is None else os.fspath(save_dir)
         return artifact.download(root=save_dir)
 
     def use_artifact(self, artifact: str, artifact_type: Optional[str] = None) -> "wandb.Artifact":
diff --git a/src/pytorch_lightning/trainer/trainer.py b/src/pytorch_lightning/trainer/trainer.py
index ea9ca7aef93b9..35606d71288a0 100644
--- a/src/pytorch_lightning/trainer/trainer.py
+++ b/src/pytorch_lightning/trainer/trainer.py
@@ -115,7 +115,7 @@ def __init__(
         logger: Union[Logger, Iterable[Logger], bool] = True,
         enable_checkpointing: bool = True,
         callbacks: Optional[Union[List[Callback], Callback]] = None,
-        default_root_dir: Optional[str] = None,
+        default_root_dir: Optional[_PATH] = None,
         gradient_clip_val: Optional[Union[int, float]] = None,
         gradient_clip_algorithm: Optional[str] = None,
         num_nodes: int = 1,
@@ -399,6 +399,9 @@ def __init__(
         log.detail(f"{self.__class__.__name__}: Initializing trainer with parameters: {locals()}")
         self.state = TrainerState()
 
+        if default_root_dir is not None:
+            default_root_dir = os.fspath(default_root_dir)
+
         # init connectors
         self._data_connector = DataConnector(self, multiple_trainloader_mode)