diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7a09a8f8f04..afd0a77ebc8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## Unreleased
 
+### Updated
+- Speed up `validate_gantt` function [[#5386](https://github.com/plotly/plotly.py/pull/5386)], with thanks to @misrasaurabh1 for the contribution!
+
 ## [6.5.0] - 2025-11-17
 
 ### Updated
diff --git a/plotly/figure_factory/_gantt.py b/plotly/figure_factory/_gantt.py
index 2fe393ffe90..006754a0ff1 100644
--- a/plotly/figure_factory/_gantt.py
+++ b/plotly/figure_factory/_gantt.py
@@ -39,12 +39,13 @@ def validate_gantt(df):
                     "following keys: {0}".format(", ".join(REQUIRED_GANTT_KEYS))
                 )
 
+        columns = {key: df[key].values for key in df}
         num_of_rows = len(df.index)
         chart = []
+        # Using only keys present in the DataFrame columns
+        keys = list(df.columns)
         for index in range(num_of_rows):
-            task_dict = {}
-            for key in df:
-                task_dict[key] = df.iloc[index][key]
+            task_dict = {key: columns[key][index] for key in keys}
             chart.append(task_dict)
 
         return chart
diff --git a/tests/test_optional/test_figure_factory/test_validate_gantt.py b/tests/test_optional/test_figure_factory/test_validate_gantt.py
new file mode 100644
index 00000000000..472a0669df2
--- /dev/null
+++ b/tests/test_optional/test_figure_factory/test_validate_gantt.py
@@ -0,0 +1,95 @@
+import pytest
+
+from plotly import exceptions, optional_imports
+from plotly.figure_factory._gantt import validate_gantt
+
+pd = optional_imports.get_module("pandas")
+
+
+@pytest.mark.parametrize("input_type", ["list", "dataframe"])
+def test_valid_with_extra_keys(input_type):
+    """Test that extra keys beyond required ones are preserved."""
+    data = [
+        {"Task": "A", "Start": "2020-01-01", "Finish": "2020-01-02", "Resource": "X"},
+        {"Task": "B", "Start": "2020-01-03", "Finish": "2020-01-04", "Resource": "Y"},
+    ]
+    if input_type == "dataframe":
+        input_data = pd.DataFrame(data)
+        result = validate_gantt(input_data)
+        assert isinstance(result, list)
+        assert set(result[0].keys()) == set(input_data.columns)
+    else:
+        input_data = data
+        result = validate_gantt(input_data)
+        assert result is input_data
+
+    assert len(result) == 2
+    assert all("Resource" in row for row in result)
+    assert set(result[0].keys()) == set(["Task", "Start", "Finish", "Resource"])
+    assert result[0]["Task"] == "A"
+    assert result[1]["Finish"] == "2020-01-04"
+
+
+def test_missing_required_key_in_dataframe():
+    df = pd.DataFrame(
+        [
+            {"Task": "A", "Start": "2020-01-01"},  # Missing "Finish"
+        ]
+    )
+    with pytest.raises(exceptions.PlotlyError):
+        validate_gantt(df)
+
+
+def test_empty_list():
+    with pytest.raises(exceptions.PlotlyError):
+        validate_gantt([])
+
+
+def test_input_is_not_list_or_dataframe():
+    with pytest.raises(exceptions.PlotlyError):
+        validate_gantt("Not a list or DataFrame")
+
+
+def test_dataframe_with_no_rows():
+    df = pd.DataFrame(columns=["Task", "Start", "Finish"])
+    result = validate_gantt(df)
+    assert isinstance(result, list)
+    assert result == []
+
+
+def test_list_with_dict_missing_all_keys():
+    input_data = [{"Resource": "X"}]
+    # Should NOT raise: list input is not validated for keys
+    result = validate_gantt(input_data)
+    assert result is input_data
+
+
+def test_large_list_with_non_dict_first_element():
+    input_data = [
+        "Not a dict",
+        *[
+            {
+                "Task": f"Task{i}",
+                "Start": f"2020-01-{i % 30 + 1:02d}",
+                "Finish": f"2020-02-{i % 28 + 1:02d}",
+            }
+            for i in range(999)
+        ],
+    ]
+    with pytest.raises(exceptions.PlotlyError):
+        validate_gantt(input_data)
+
+
+def test_dataframe_column_order_and_index():
+    df = pd.DataFrame(
+        [
+            {"Finish": "2023-01-02", "Start": "2023-01-01", "Task": "A"},
+            {"Finish": "2023-01-03", "Start": "2023-01-02", "Task": "B"},
+        ],
+        index=["x", "y"],
+    )
+    result = validate_gantt(df)
+    assert len(result) == 2
+    # Ensure values preserved regardless of order/index
+    assert result[0]["Task"] == "A"
+    assert set(result[0].keys()) == set(["Task", "Start", "Finish"])