diff --git a/awswrangler/neptune/_neptune.py b/awswrangler/neptune/_neptune.py
index 952d741fe..f840a08cd 100644
--- a/awswrangler/neptune/_neptune.py
+++ b/awswrangler/neptune/_neptune.py
@@ -170,7 +170,7 @@ def to_property_graph(
     ... )
     """
     # check if ~id and ~label column exist and if not throw error
-    g = gremlin.traversal().withGraph(gremlin.Graph())
+    g = gremlin.Graph().traversal()
     is_edge_df = False
     is_update_df = True
     if "~id" in df.columns:
@@ -203,6 +203,24 @@ def to_property_graph(
     return _run_gremlin_insert(client, g)
 
 
+# SPARQL 1.1 IRIREF grammar: '<' ([^<>"{}|^`\]-[#x00-#x20])* '>'
+# A cell value spliced between '<' and '>' must contain only the characters allowed
+# inside the IRIREF token. Anything else can close the token and inject arbitrary
+# SPARQL UPDATE syntax (DELETE / DROP / LOAD / ...).
+_IRIREF_INNER_RE = re.compile(r"^[^\x00-\x20<>\"{}|^`\\]*$")
+
+
+def _validate_iriref_cell(value: Any, column: str, row_index: int) -> str:
+    text = str(value)
+    if not _IRIREF_INNER_RE.match(text):
+        raise exceptions.InvalidArgumentValue(
+            f"Value in column {column!r} at row index {row_index} is not a valid IRI: "
+            f"{text!r}. Cells written by `to_rdf_graph` must conform to the SPARQL "
+            'IRIREF grammar (no whitespace, control characters, or any of <>"{}|^`\\).'
+        )
+    return text
+
+
 @_utils.check_optional_dependency(sparql, "SPARQLWrapper")
 def to_rdf_graph(
     client: NeptuneClient,
@@ -267,14 +285,18 @@ def to_rdf_graph(
     query = ""
     # Loop through items in the DF
     for i, (_, row) in enumerate(df.iterrows()):
+        subject = _validate_iriref_cell(row[subject_column], subject_column, i)
+        predicate = _validate_iriref_cell(row[predicate_column], predicate_column, i)
+        obj = _validate_iriref_cell(row[object_column], object_column, i)
         # build up a query
         if is_quads:
-            insert = f"""INSERT DATA {{ GRAPH <{row[graph_column]}> {{<{row[subject_column]}>
-                    <{str(row[predicate_column])}> <{row[object_column]}> . }} }}; """
+            graph = _validate_iriref_cell(row[graph_column], graph_column, i)
+            insert = f"""INSERT DATA {{ GRAPH <{graph}> {{<{subject}>
+                    <{predicate}> <{obj}> . }} }}; """
             query = query + insert
         else:
-            insert = f"""INSERT DATA {{ <{row[subject_column]}> <{str(row[predicate_column])}>
-                    <{row[object_column]}> . }}; """
+            insert = f"""INSERT DATA {{ <{subject}> <{predicate}>
+                    <{obj}> . }}; """
             query = query + insert
         # run the query
         if i > 0 and i % batch_size == 0:
diff --git a/tests/unit/test_neptune_parsing.py b/tests/unit/test_neptune_parsing.py
index a7ed7494d..cdc1fb8d5 100644
--- a/tests/unit/test_neptune_parsing.py
+++ b/tests/unit/test_neptune_parsing.py
@@ -1,4 +1,5 @@
 import logging
+from unittest.mock import MagicMock
 
 import pytest  # type: ignore
 from gremlin_python.process.traversal import T
@@ -6,6 +7,8 @@
 
 import awswrangler as wr
 import awswrangler.pandas as pd
+from awswrangler import exceptions
+from awswrangler.neptune._client import NeptuneClient
 
 logging.getLogger("awswrangler").setLevel(logging.DEBUG)
 
@@ -29,7 +32,7 @@ def test_parse_gremlin_vertex_elements(gremlin_parser):
     assert df.shape == (1, 3)
     assert row["id"] == "foo"
     assert row["label"] == "vertex"
-    assert row["properties"] is None
+    assert not row["properties"]  # gremlinpython <3.8 returns None, >=3.8 returns []
 
     # parse multiple vertex elements
     v1 = Vertex("bar")
@@ -40,7 +43,7 @@ def test_parse_gremlin_vertex_elements(gremlin_parser):
     assert df.shape == (2, 3)
     assert row["id"] == "bar"
     assert row["label"] == "vertex"
-    assert row["properties"] is None
+    assert not row["properties"]  # gremlinpython <3.8 returns None, >=3.8 returns []
 
 
 # parse Edge elements
@@ -56,7 +59,7 @@ def test_parse_gremlin_edge_elements(gremlin_parser):
     assert row["outV"] == "out1"
     assert row["label"] == "label"
     assert row["inV"] == "in1"
-    assert row["properties"] is None
+    assert not row["properties"]  # gremlinpython <3.8 returns None, >=3.8 returns []
 
     # parse multiple edge elements
     v1 = Edge("bar", "out1", "label", "in2")
@@ -69,7 +72,7 @@ def test_parse_gremlin_edge_elements(gremlin_parser):
     assert row["outV"] == "out1"
     assert row["label"] == "label"
     assert row["inV"] == "in2"
-    assert row["properties"] is None
+    assert not row["properties"]  # gremlinpython <3.8 returns None, >=3.8 returns []
 
 
 # parse Property elements
@@ -86,7 +89,7 @@ def test_parse_gremlin_property_elements(gremlin_parser):
     assert row["value"] == "bar"
     assert row["key"] == "name"
     assert row["vertex"] == "v1"
-    assert row["properties"] is None
+    assert not row["properties"]  # gremlinpython <3.8 returns None, >=3.8 returns []
 
     v = Property("foo", "name", "bar")
     input = [v]
@@ -100,6 +103,11 @@ def test_parse_gremlin_property_elements(gremlin_parser):
 
 
 # parse Path elements
+def _normalize_properties(d: dict) -> dict:
+    # gremlinpython <3.8 returns properties=None, >=3.8 returns properties=[].
+    return {k: (None if k == "properties" and not v else v) for k, v in d.items()}
+
+
 def test_parse_gremlin_path_elements(gremlin_parser):
     # parse path with elements
     v = Vertex("foo")
@@ -110,9 +118,15 @@ def test_parse_gremlin_path_elements(gremlin_parser):
     df = pd.DataFrame.from_records(out)
     row = df.iloc[0]
     assert df.shape == (1, 3)
-    assert row[0] == {"id": "foo", "label": "vertex", "properties": None}
-    assert row[1] == {"id": "e1", "label": "label", "outV": "foo", "inV": "bar", "properties": None}
-    assert row[2] == {"id": "bar", "label": "vertex", "properties": None}
+    assert _normalize_properties(row[0]) == {"id": "foo", "label": "vertex", "properties": None}
+    assert _normalize_properties(row[1]) == {
+        "id": "e1",
+        "label": "label",
+        "outV": "foo",
+        "inV": "bar",
+        "properties": None,
+    }
+    assert _normalize_properties(row[2]) == {"id": "bar", "label": "vertex", "properties": None}
 
     # parse path with multiple elements
     e2 = Edge("bar", "out1", "label", "in2")
@@ -122,9 +136,15 @@ def test_parse_gremlin_path_elements(gremlin_parser):
     df = pd.DataFrame.from_records(out)
     row = df.iloc[1]
     assert df.shape == (2, 3)
-    assert row[0] == {"id": "bar", "label": "vertex", "properties": None}
-    assert row[1] == {"id": "bar", "label": "label", "outV": "out1", "inV": "in2", "properties": None}
-    assert row[2] == {"id": "in2", "label": "vertex", "properties": None}
+    assert _normalize_properties(row[0]) == {"id": "bar", "label": "vertex", "properties": None}
+    assert _normalize_properties(row[1]) == {
+        "id": "bar",
+        "label": "label",
+        "outV": "out1",
+        "inV": "in2",
+        "properties": None,
+    }
+    assert _normalize_properties(row[2]) == {"id": "in2", "label": "vertex", "properties": None}
 
     # parse path with maps
     p = Path(
@@ -152,7 +172,13 @@ def test_parse_gremlin_path_elements(gremlin_parser):
     assert df.shape == (1, 3)
     assert row[0]["name"] == "foo"
     assert row[0]["age"] == 29
-    assert row[1] == {"id": "bar", "label": "label", "outV": "out1", "inV": "in2", "properties": None}
+    assert _normalize_properties(row[1]) == {
+        "id": "bar",
+        "label": "label",
+        "outV": "out1",
+        "inV": "in2",
+        "properties": None,
+    }
     assert row[2]["name"] == "bar"
     assert row[2]["age"] == 40
 
@@ -216,3 +242,92 @@ def test_parse_gremlin_subgraph(gremlin_parser):
     assert df.shape == (1, 2)
     assert row["@type"] == "tinker:graph"
     assert row["@value"] == {"vertices": ["v[45]", "v[9]"], "edges": ["e[3990][9-route->45]"]}
+
+
+# to_rdf_graph IRIREF validation: caller-supplied DataFrame cells must conform to
+# the SPARQL IRIREF grammar so they cannot close the <...> token and inject
+# arbitrary SPARQL UPDATE syntax (DELETE / DROP / LOAD / ...).
+
+
+def _rdf_triples_df() -> pd.DataFrame:
+    return pd.DataFrame(
+        {
+            "s": ["http://example.org/alice", "http://example.org/bob"],
+            "p": ["http://xmlns.com/foaf/0.1/name", "http://xmlns.com/foaf/0.1/name"],
+            "o": ["http://example.org/AliceName", "http://example.org/BobName"],
+        }
+    )
+
+
+def _mock_neptune_client() -> MagicMock:
+    client = MagicMock(spec=NeptuneClient)
+    client.write_sparql.return_value = True
+    return client
+
+
+def test_to_rdf_graph_accepts_well_formed_iris():
+    client = _mock_neptune_client()
+    df = _rdf_triples_df()
+
+    assert wr.neptune.to_rdf_graph(client, df) is True
+    client.write_sparql.assert_called_once()
+    query = client.write_sparql.call_args.args[0]
+    assert "<http://example.org/alice>" in query
+    assert "<http://example.org/bob>" in query
+
+
+@pytest.mark.parametrize(
+    "malicious_cell, column",
+    [
+        # Bug-bounty PoC payload: closes IRI, runs DELETE WHERE, reopens INSERT.
+        (
+            "> . }; DELETE WHERE { ?s ?p ?o }; "
+            "INSERT DATA { <http://evil.com/x> <http://evil.com/y> <http://evil.com/z",
+            "o",
+        ),
+        # DROP ALL via the subject slot.
+        ("http://x.com/s> <http://x.com/p> <http://x.com/o> . }; DROP ALL ; INSERT DATA { <a", "s"),
+        # LOAD via the predicate slot.
+        (
+            "http://x.com/p> <http://x.com/o> . }; LOAD <http://evil.com/payload.ttl> ; "
+            "INSERT DATA { <http://x.com/s> <http://x.com/p2",
+            "p",
+        ),
+        # Whitespace alone is enough to break the IRIREF token.
+        ("http://example.org/ has space", "o"),
+        ("http://example.org/a\n<http://x>", "o"),
+        ("http://example.org/<inner>", "s"),
+    ],
+)
+def test_to_rdf_graph_rejects_malicious_cells(malicious_cell, column):
+    client = _mock_neptune_client()
+    df = _rdf_triples_df()
+    df.loc[0, column] = malicious_cell
+
+    with pytest.raises(exceptions.InvalidArgumentValue, match="not a valid IRI"):
+        wr.neptune.to_rdf_graph(client, df)
+    # Validation must run before any network call.
+    client.write_sparql.assert_not_called()
+
+
+def test_to_rdf_graph_rejects_malicious_graph_column_for_quads():
+    client = _mock_neptune_client()
+    df = _rdf_triples_df()
+    df["g"] = ["http://example.org/g1", "http://example.org/g2"]
+    df.loc[0, "g"] = "http://x> {} }; DROP ALL ; INSERT DATA { GRAPH <http://x> { <a"
+
+    with pytest.raises(exceptions.InvalidArgumentValue, match="'g'"):
+        wr.neptune.to_rdf_graph(client, df)
+    client.write_sparql.assert_not_called()
+
+
+def test_to_rdf_graph_error_identifies_row_and_column():
+    client = _mock_neptune_client()
+    df = _rdf_triples_df()
+    df.loc[1, "o"] = "http://example.org/bad value"
+
+    with pytest.raises(exceptions.InvalidArgumentValue) as exc_info:
+        wr.neptune.to_rdf_graph(client, df)
+    message = str(exc_info.value)
+    assert "'o'" in message
+    assert "row index 1" in message