diff --git a/README.md b/README.md
index a71df0c1b..cb8144442 100644
--- a/README.md
+++ b/README.md
@@ -58,3 +58,4 @@ Please also cite one of the following papers to credit BIDS, depending on which
 - [EEG-BIDS](https://doi.org/10.1038/s41597-019-0104-8)
 - [iEEG-BIDS](https://doi.org/10.1038/s41597-019-0105-7)
 - [NIRS-BIDS](https://doi.org/10.31219/osf.io/7nmcp)
+- [Motion-BIDS](https://doi.org/10.1038/s41597-024-03559-8)
diff --git a/doc/authors.rst b/doc/authors.rst
index da3cf8631..97df068e2 100644
--- a/doc/authors.rst
+++ b/doc/authors.rst
@@ -59,3 +59,4 @@
 .. _waldie11: https://github.com/waldie11
 .. _William Turner: https://bootstrapbill.github.io/
 .. _Yorguin Mantilla: https://github.com/yjmantilla
+.. _Julius Welzel: https://github.com/JuliusWelzel
diff --git a/doc/whats_new.rst b/doc/whats_new.rst
index 476bf7f31..fd7e7a938 100644
--- a/doc/whats_new.rst
+++ b/doc/whats_new.rst
@@ -19,11 +19,13 @@ Version 0.18 (unreleased)
 
 The following authors contributed for the first time. Thank you so much! 🤩
 
+* `Julius Welzel`_
 * `Alex Lopez Marquez`_
 
+
 The following authors had contributed before. Thank you for sticking around! 🤘
 
-* TBD
+* `Stefan Appelhoff`_
 
 
 Detailed list of changes
@@ -33,11 +35,12 @@ Detailed list of changes
 ^^^^^^^^^^^^^^^
 
 - :func:`mne_bids.write_raw_bids()` has a new parameter `electrodes_tsv_task` which allows adding the `task` entity to the `electrodes.tsv` filepath, by `Alex Lopez Marquez`_ (:gh:`1424`)
+- Extended the configuration to recognise `motion` as a valid BIDS datatype by `Julius Welzel`_ (:gh:`1430`)
 
 🧐 API and behavior changes
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-- None yet
+-  `tracksys` accepted as argument in :class:`mne_bids.BIDSPath()` by `Julius Welzel`_ (:gh:`1430`)
 
 🛠 Requirements
 ^^^^^^^^^^^^^^^
diff --git a/mne_bids/config.py b/mne_bids/config.py
index 5888f3f11..5e356bf21 100644
--- a/mne_bids/config.py
+++ b/mne_bids/config.py
@@ -6,7 +6,7 @@
 from mne import io
 from mne.io.constants import FIFF
 
-BIDS_VERSION = "1.7.0"
+BIDS_VERSION = "1.9.0"
 
 PYBV_VERSION = "0.7.3"
 EEGLABIO_VERSION = "0.0.2"
@@ -15,17 +15,19 @@
 
 EPHY_ALLOWED_DATATYPES = ["meg", "eeg", "ieeg", "nirs"]
 
-ALLOWED_DATATYPES = EPHY_ALLOWED_DATATYPES + ["anat", "beh"]
+ALLOWED_DATATYPES = EPHY_ALLOWED_DATATYPES + ["anat", "beh", "motion"]
 
 MEG_CONVERT_FORMATS = ["FIF", "auto"]
 EEG_CONVERT_FORMATS = ["BrainVision", "auto"]
 IEEG_CONVERT_FORMATS = ["BrainVision", "auto"]
 NIRS_CONVERT_FORMATS = ["auto"]
+MOTION_CONVERT_FORMATS = ["tsv", "auto"]
 CONVERT_FORMATS = {
     "meg": MEG_CONVERT_FORMATS,
     "eeg": EEG_CONVERT_FORMATS,
     "ieeg": IEEG_CONVERT_FORMATS,
     "nirs": NIRS_CONVERT_FORMATS,
+    "motion": MOTION_CONVERT_FORMATS,
 }
 
 # Orientation of the coordinate system dependent on manufacturer
@@ -147,12 +149,17 @@
     ".snirf",  # SNIRF
 ]
 
+allowed_extensions_motion = [
+    ".tsv",  # Tab-separated values
+]
+
 # allowed extensions (data formats) in BIDS spec
 ALLOWED_DATATYPE_EXTENSIONS = {
     "meg": allowed_extensions_meg,
     "eeg": allowed_extensions_eeg,
     "ieeg": allowed_extensions_ieeg,
     "nirs": allowed_extensions_nirs,
+    "motion": allowed_extensions_motion,
 }
 
 # allow additional extensions that are not BIDS
@@ -190,6 +197,7 @@
     "physio",
     "stim",  # behavioral
     "nirs",
+    "motion",  # motion
 ]
 
 # converts suffix to known path modalities
@@ -227,6 +235,7 @@
     "description",
     "suffix",
     "extension",
+    "tracking_system",
 )
 ALLOWED_PATH_ENTITIES_SHORT = {
     "sub": "subject",
@@ -239,6 +248,7 @@
     "recording": "recording",
     "split": "split",
     "desc": "description",
+    "tracksys": "tracking_system",
 }
 
 # Annotations to never remove during reading or writing
@@ -316,6 +326,7 @@
 ALLOWED_SPACES["ieeg"] = BIDS_SHARED_COORDINATE_FRAMES + BIDS_IEEG_COORDINATE_FRAMES
 ALLOWED_SPACES["anat"] = None
 ALLOWED_SPACES["beh"] = None
+ALLOWED_SPACES["motion"] = None
 
 # See: https://bids-specification.readthedocs.io/en/latest/appendices/entity-table.html#encephalography-eeg-ieeg-and-meg  # noqa: E501
 ENTITY_VALUE_TYPE = {
@@ -331,6 +342,7 @@
     "description": "label",
     "suffix": "label",
     "extension": "label",
+    "tracking_system": "label",
 }
 
 # mapping from supported BIDs coordinate frames -> MNE
diff --git a/mne_bids/path.py b/mne_bids/path.py
index bcfed1816..f3329880f 100644
--- a/mne_bids/path.py
+++ b/mne_bids/path.py
@@ -385,6 +385,7 @@ def __init__(
         space=None,
         split=None,
         description=None,
+        tracking_system=None,
         root=None,
         suffix=None,
         extension=None,
@@ -421,6 +422,7 @@ def __init__(
             space=space,
             split=split,
             description=description,
+            tracking_system=tracking_system,
             root=root,
             datatype=datatype,
             suffix=suffix,
@@ -442,6 +444,7 @@ def entities(self):
             "recording": self.recording,
             "split": self.split,
             "description": self.description,
+            "tracking_system": self.tracking_system,
         }
 
     @property
@@ -575,6 +578,15 @@ def description(self) -> str | None:
     def description(self, value):
         self.update(description=value)
 
+    @property
+    def tracking_system(self) -> str | None:
+        """The tracking system entity."""
+        return self._tracking_system
+
+    @tracking_system.setter
+    def tracking_system(self, value):
+        self.update(tracking_system=value)
+
     @property
     def suffix(self) -> str | None:
         """The filename suffix."""
@@ -881,7 +893,9 @@ def fpath(self):
                 if self.suffix is None or self.suffix in ALLOWED_DATATYPES:
                     # now only use valid datatype extension
                     if self.extension is None:
-                        valid_exts = sum(ALLOWED_DATATYPE_EXTENSIONS.values(), [])
+                        valid_exts = ALLOWED_DATATYPE_EXTENSIONS.get(
+                            self.datatype, sum(ALLOWED_DATATYPE_EXTENSIONS.values(), [])
+                        )
                     else:
                         valid_exts = [self.extension]
                     matching_paths = [
@@ -2325,6 +2339,7 @@ def _filter_fnames(
     description=None,
     suffix=None,
     extension=None,
+    tracking_system=None,
 ):
     """Filter a list of BIDS filenames / paths based on BIDS entity values.
 
@@ -2351,6 +2366,7 @@ def _filter_fnames(
     description = _ensure_tuple(description)
     suffix = _ensure_tuple(suffix)
     extension = _ensure_tuple(extension)
+    tracking_system = _ensure_tuple(tracking_system)
 
     leading_path_str = r".*\/?"  # nothing or something ending with a `/`
     sub_str = r"sub-(" + "|".join(subject) + ")" if subject else r"sub-([^_]+)"
@@ -2375,6 +2391,11 @@ def _filter_fnames(
     )
     suffix_str = r"_(" + "|".join(suffix) + ")" if suffix else r"_([^_]+)"
     ext_str = r"(" + "|".join(extension) + ")$" if extension else r"\.([^_]+)"
+    tracksys_str = (
+        r"tracksys-(" + "|".join(tracking_system) + ")"
+        if tracking_system
+        else r"(|tracksys-([^_]+))"
+    )
 
     regexp = (
         leading_path_str
@@ -2390,6 +2411,7 @@ def _filter_fnames(
         + desc_str
         + suffix_str
         + ext_str
+        + tracksys_str
     )
 
     # Convert to str so we can apply the regexp ...
diff --git a/mne_bids/tests/test_path.py b/mne_bids/tests/test_path.py
index acd51a956..effbb1644 100644
--- a/mne_bids/tests/test_path.py
+++ b/mne_bids/tests/test_path.py
@@ -500,6 +500,7 @@ def test_get_entities_from_fname(fname):
         "recording",
         "split",
         "description",
+        "tracking_system",
     ]
 
 
@@ -537,6 +538,7 @@ def test_get_entities_from_fname_errors(fname):
         "recording",
         "split",
         "description",
+        "tracking_system",
     ]
 
     assert params["subject"] == "01"