diff --git a/docx-core/examples/sdt.rs b/docx-core/examples/sdt.rs
new file mode 100644
index 0000000..1bfdf35
--- /dev/null
+++ b/docx-core/examples/sdt.rs
@@ -0,0 +1,16 @@
+use docx_rs::*;
+
+pub fn main() -> Result<(), DocxError> {
+    let path = std::path::Path::new("./output/sdt.docx");
+    let file = std::fs::File::create(&path).unwrap();
+    let p = Paragraph::new().add_run(
+        Run::new()
+            .add_text("Hello")
+            .fonts(RunFonts::new().ascii("Arial")),
+    );
+    Docx::new()
+        .add_structured_data_tag(StructuredDataTag::new().add_paragraph(p))
+        .build()
+        .pack(file)?;
+    Ok(())
+}
diff --git a/docx-core/src/documents/document.rs b/docx-core/src/documents/document.rs
index 374cd38..0a4c468 100644
--- a/docx-core/src/documents/document.rs
+++ b/docx-core/src/documents/document.rs
@@ -21,6 +21,7 @@ pub enum DocumentChild {
     BookmarkEnd(BookmarkEnd),
     CommentStart(Box<CommentRangeStart>),
     CommentEnd(CommentRangeEnd),
+    StructuredDataTag(StructuredDataTag),
 }
 
 impl Serialize for DocumentChild {
@@ -65,6 +66,12 @@ impl Serialize for DocumentChild {
                 t.serialize_field("data", r)?;
                 t.end()
             }
+            DocumentChild::StructuredDataTag(ref r) => {
+                let mut t = serializer.serialize_struct("StructuredDataTag", 2)?;
+                t.serialize_field("type", "structuredDataTag")?;
+                t.serialize_field("data", r)?;
+                t.end()
+            }
         }
     }
 }
@@ -179,6 +186,14 @@ impl Document {
         self.section_property = self.section_property.even_footer(h, rid);
         self
     }
+
+    pub fn add_structured_data_tag(mut self, t: StructuredDataTag) -> Self {
+        if t.has_numbering {
+            self.has_numbering = true
+        }
+        self.children.push(DocumentChild::StructuredDataTag(t));
+        self
+    }
 }
 
 impl BuildXML for DocumentChild {
@@ -190,6 +205,7 @@ impl BuildXML for DocumentChild {
             DocumentChild::BookmarkEnd(v) => v.build(),
             DocumentChild::CommentStart(v) => v.build(),
             DocumentChild::CommentEnd(v) => v.build(),
+            DocumentChild::StructuredDataTag(v) => v.build(),
         }
     }
 }
diff --git a/docx-core/src/documents/elements/mod.rs b/docx-core/src/documents/elements/mod.rs
index 224ba1c..73eb3e6 100644
--- a/docx-core/src/documents/elements/mod.rs
+++ b/docx-core/src/documents/elements/mod.rs
@@ -23,9 +23,9 @@ mod doc_id;
 mod doc_var;
 mod drawing;
 mod font;
+mod footer_reference;
 mod grid_span;
 mod header_reference;
-mod footer_reference;
 mod highlight;
 mod indent;
 mod indent_level;
@@ -62,6 +62,7 @@ mod section;
 mod section_property;
 mod shading;
 mod start;
+mod structured_data_tag;
 mod style;
 mod sz;
 mod sz_cs;
@@ -120,9 +121,9 @@ pub use doc_id::*;
 pub use doc_var::*;
 pub use drawing::*;
 pub use font::*;
+pub use footer_reference::*;
 pub use grid_span::*;
 pub use header_reference::*;
-pub use footer_reference::*;
 pub use highlight::*;
 pub use indent::*;
 pub use indent_level::*;
@@ -159,6 +160,7 @@ pub use section::*;
 pub use section_property::*;
 pub use shading::*;
 pub use start::*;
+pub use structured_data_tag::*;
 pub use style::*;
 pub use sz::*;
 pub use sz_cs::*;
diff --git a/docx-core/src/documents/elements/structured_data_tag.rs b/docx-core/src/documents/elements/structured_data_tag.rs
new file mode 100644
index 0000000..f602188
--- /dev/null
+++ b/docx-core/src/documents/elements/structured_data_tag.rs
@@ -0,0 +1,118 @@
+use serde::ser::{SerializeStruct, Serializer};
+use serde::Serialize;
+
+use super::*;
+use crate::documents::BuildXML;
+// use crate::types::*;
+use crate::xml_builder::*;
+
+#[derive(Serialize, Debug, Clone, PartialEq)]
+#[serde(rename_all = "camelCase")]
+pub struct StructuredDataTag {
+    pub children: Vec<StructuredDataTagChild>,
+    pub has_numbering: bool,
+}
+
+impl Default for StructuredDataTag {
+    fn default() -> Self {
+        Self {
+            children: Vec::new(),
+            has_numbering: false,
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum StructuredDataTagChild {
+    Run(Box<Run>),
+    Paragraph(Box<Paragraph>),
+}
+
+impl BuildXML for StructuredDataTagChild {
+    fn build(&self) -> Vec<u8> {
+        match self {
+            StructuredDataTagChild::Run(v) => v.build(),
+            StructuredDataTagChild::Paragraph(v) => v.build(),
+        }
+    }
+}
+
+impl Serialize for StructuredDataTagChild {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        match *self {
+            StructuredDataTagChild::Run(ref r) => {
+                let mut t = serializer.serialize_struct("Run", 2)?;
+                t.serialize_field("type", "run")?;
+                t.serialize_field("data", r)?;
+                t.end()
+            }
+            StructuredDataTagChild::Paragraph(ref r) => {
+                let mut t = serializer.serialize_struct("Paragraph", 2)?;
+                t.serialize_field("type", "paragraph")?;
+                t.serialize_field("data", r)?;
+                t.end()
+            }
+        }
+    }
+}
+
+impl StructuredDataTag {
+    pub fn new() -> Self {
+        Default::default()
+    }
+
+    pub fn add_run(mut self, run: Run) -> Self {
+        self.children
+            .push(StructuredDataTagChild::Run(Box::new(run)));
+        self
+    }
+
+    pub fn add_paragraph(mut self, p: Paragraph) -> Self {
+        if p.has_numbering {
+            self.has_numbering = true
+        }
+        self.children
+            .push(StructuredDataTagChild::Paragraph(Box::new(p)));
+        self
+    }
+}
+
+impl BuildXML for StructuredDataTag {
+    fn build(&self) -> Vec<u8> {
+        XMLBuilder::new()
+            .open_structured_tag()
+            .open_structured_tag_property()
+            .close()
+            .open_structured_tag_content()
+            .add_children(&self.children)
+            .close()
+            .close()
+            .build()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+
+    use super::*;
+    #[cfg(test)]
+    use pretty_assertions::assert_eq;
+    use std::str;
+
+    #[test]
+    fn test_sdt() {
+        let b = StructuredDataTag::new()
+            .add_run(Run::new().add_text("Hello"))
+            .build();
+        assert_eq!(
+            str::from_utf8(&b).unwrap(),
+            r#"<w:sdt>
+  <w:sdtPr />
+  <w:sdtContent><w:r><w:rPr /><w:t xml:space="preserve">Hello</w:t></w:r></w:sdtContent>
+</w:sdt>"#
+        );
+    }
+}
diff --git a/docx-core/src/documents/mod.rs b/docx-core/src/documents/mod.rs
index 49588e0..217dd5f 100644
--- a/docx-core/src/documents/mod.rs
+++ b/docx-core/src/documents/mod.rs
@@ -191,6 +191,16 @@ impl Docx {
         self
     }
 
+    pub fn add_structured_data_tag(mut self, t: StructuredDataTag) -> Docx {
+        if t.has_numbering {
+            // If this document has numbering, set numberings.xml to document_rels.
+            // This is because numberings.xml without numbering cause an error on word online.
+            self.document_rels.has_numberings = true;
+        }
+        self.document = self.document.add_structured_data_tag(t);
+        self
+    }
+
     pub fn add_bookmark_start(mut self, id: usize, name: impl Into<String>) -> Docx {
         self.document = self.document.add_bookmark_start(id, name);
         self
diff --git a/docx-core/src/xml_builder/elements.rs b/docx-core/src/xml_builder/elements.rs
index a3cf268..c7389da 100644
--- a/docx-core/src/xml_builder/elements.rs
+++ b/docx-core/src/xml_builder/elements.rs
@@ -72,6 +72,11 @@ impl XMLBuilder {
     open!(open_paragraph, "w:p", "w14:paraId");
     open!(open_paragraph_property, "w:pPr");
     open!(open_doc_defaults, "w:docDefaults");
+
+    open!(open_structured_tag, "w:sdt");
+    open!(open_structured_tag_content, "w:sdtContent");
+    open!(open_structured_tag_property, "w:sdtPr");
+
     // i.e. <w:outlineLvl ...>
     closed_with_usize!(outline_lvl, "w:outlineLvl");
     // i.e. <w:name ... >