diff --git a/src/reader/xlsx/workbook_rels.rs b/src/reader/xlsx/workbook_rels.rs
index 53185210..815bdb24 100644
--- a/src/reader/xlsx/workbook_rels.rs
+++ b/src/reader/xlsx/workbook_rels.rs
@@ -1,8 +1,12 @@
 use std::io;
 
 use quick_xml::{
-    Reader,
+    NsReader,
     events::Event,
+    name::{
+        Namespace,
+        ResolveResult,
+    },
 };
 
 use super::{
@@ -16,6 +20,7 @@ use crate::{
     helper::const_str::{
         PIVOT_CACHE_DEF_NS,
         PKG_WORKBOOK_RELS,
+        REL_NS,
     },
     structs::Workbook,
 };
@@ -25,7 +30,7 @@ pub(crate) fn read<R: io::Read + io::Seek>(
     wb: &mut Workbook,
 ) -> Result<Vec<(String, String, String)>, XlsxError> {
     let r = io::BufReader::new(super::driver::zip_by_name(arv, PKG_WORKBOOK_RELS)?);
-    let mut reader = Reader::from_reader(r);
+    let mut reader = NsReader::from_reader(r);
     reader.config_mut().trim_text(true);
 
     let mut result: Vec<(String, String, String)> = Vec::new();
@@ -33,7 +38,10 @@ pub(crate) fn read<R: io::Read + io::Seek>(
     xml_read_loop!(
         reader,
         Event::Empty(ref e) => {
-            if e.name().into_inner() == b"Relationship" {
+            let (namespace, local_name) = reader.resolver().resolve_element(e.name());
+            if namespace == ResolveResult::Bound(Namespace(REL_NS.as_bytes()))
+                && local_name.as_ref() == b"Relationship"
+            {
                 let id_value = get_attribute(e, b"Id").unwrap();
                 let type_value = get_attribute(e, b"Type").unwrap();
                 let target_value = get_attribute(e, b"Target").unwrap();
@@ -52,3 +60,74 @@ pub(crate) fn read<R: io::Read + io::Seek>(
 
     Ok(result)
 }
+
+#[cfg(test)]
+mod tests {
+    use std::io::{
+        Cursor,
+        Write,
+    };
+
+    use rstest::rstest;
+    use zip::{
+        ZipArchive,
+        ZipWriter,
+        write::SimpleFileOptions,
+    };
+
+    use super::*;
+
+    fn relationships(xml: &str) -> Vec<(String, String, String)> {
+        let mut zip = ZipWriter::new(Cursor::new(Vec::new()));
+        zip.start_file(PKG_WORKBOOK_RELS, SimpleFileOptions::default())
+            .unwrap();
+        zip.write_all(xml.as_bytes()).unwrap();
+        let mut archive = ZipArchive::new(zip.finish().unwrap()).unwrap();
+        read(&mut archive, &mut Workbook::default()).unwrap()
+    }
+
+    #[rstest]
+    #[case("")]
+    #[case("ns0:")]
+    #[case("pkg:")]
+    fn relationship_namespace_accepts_equivalent_spellings(#[case] prefix: &str) {
+        let declaration = if prefix.is_empty() {
+            "xmlns".to_string()
+        } else {
+            format!("xmlns:{}", prefix.trim_end_matches(':'))
+        };
+        let xml = format!(
+            "<{prefix}Relationships {declaration}=\"{REL_NS}\"><{prefix}Relationship Id=\"rId1\" \
+             Type=\"worksheet\" Target=\"/xl/worksheets/sheet1.xml\"/></{prefix}Relationships>"
+        );
+        assert_eq!(
+            relationships(&xml),
+            vec![(
+                "rId1".to_string(),
+                "worksheet".to_string(),
+                "worksheets/sheet1.xml".to_string(),
+            )]
+        );
+    }
+
+    #[rstest]
+    #[case(r#"<Relationship xmlns="urn:unrelated"/>"#)]
+    #[case(r#"<other:Relationship xmlns:other="urn:unrelated"/>"#)]
+    #[case(r#"<Relationship xmlns=""/>"#)]
+    #[case("<Other/>")]
+    fn unrelated_relationship_names_are_not_interpreted(#[case] child: &str) {
+        let xml = format!(r#"<Relationships xmlns="{REL_NS}">{child}</Relationships>"#);
+        assert!(relationships(&xml).is_empty());
+    }
+
+    #[test]
+    fn child_namespace_declarations_are_resolved_in_scope() {
+        let xml = format!(
+            "<Relationships xmlns=\"{REL_NS}\" \
+             xmlns:p=\"urn:unrelated\"><p:Relationship/><p:Relationship xmlns:p=\"{REL_NS}\" \
+             Id=\"rId1\" Type=\"worksheet\" \
+             Target=\"worksheets/sheet1.xml\"/><p:Relationship/></Relationships>"
+        );
+        assert_eq!(relationships(&xml).len(), 1);
+    }
+}
diff --git a/tests/workbook_relationship_namespaces.rs b/tests/workbook_relationship_namespaces.rs
new file mode 100644
index 00000000..4e0e09ec
--- /dev/null
+++ b/tests/workbook_relationship_namespaces.rs
@@ -0,0 +1,77 @@
+//! Workbook relationships must be resolved by namespace, not prefix spelling.
+use std::io::{
+    Cursor,
+    Read,
+    Write,
+};
+
+use rstest::rstest;
+use umya_spreadsheet::{
+    Border,
+    reader,
+    writer,
+};
+use zip::{
+    ZipArchive,
+    ZipWriter,
+    write::SimpleFileOptions,
+};
+
+fn workbook_with_relationship_prefix(prefix: &str) -> Vec<u8> {
+    let mut book = umya_spreadsheet::new_file();
+    let sheet = book.sheet_mut(0).unwrap();
+    sheet.cell_mut("A1").set_value("Namespace regression");
+    sheet.cell_mut("B2").set_value_number(42);
+    sheet.style_mut("A1").font_mut().set_bold(true);
+    sheet
+        .style_mut("A1")
+        .borders_mut()
+        .bottom_mut()
+        .set_border_style(Border::BORDER_THIN);
+
+    let mut original = Vec::new();
+    writer::xlsx::write_writer(&book, &mut original).unwrap();
+    let mut source = ZipArchive::new(Cursor::new(original)).unwrap();
+    let mut output = ZipWriter::new(Cursor::new(Vec::new()));
+    for index in 0..source.len() {
+        let mut part = source.by_index(index).unwrap();
+        let mut bytes = Vec::new();
+        part.read_to_end(&mut bytes).unwrap();
+        if part.name() == "xl/_rels/workbook.xml.rels" && !prefix.is_empty() {
+            let xml = String::from_utf8(bytes).unwrap();
+            bytes = xml
+                .replace("<Relationship", &format!("<{prefix}:Relationship"))
+                .replace("</Relationships>", &format!("</{prefix}:Relationships>"))
+                .replace("xmlns=", &format!("xmlns:{prefix}="))
+                .into_bytes();
+        }
+        output
+            .start_file(part.name(), SimpleFileOptions::default())
+            .unwrap();
+        output.write_all(&bytes).unwrap();
+    }
+    output.finish().unwrap().into_inner()
+}
+
+#[rstest]
+#[case("")]
+#[case("ns0")]
+#[case("pkg")]
+fn workbook_relationship_prefix_preserves_cells_and_styles(#[case] prefix: &str) {
+    let bytes = workbook_with_relationship_prefix(prefix);
+    let book = reader::xlsx::read_reader(Cursor::new(bytes), true).unwrap();
+    for book in [book.clone(), {
+        let mut output = Vec::new();
+        writer::xlsx::write_writer(&book, &mut output).unwrap();
+        reader::xlsx::read_reader(Cursor::new(output), true).unwrap()
+    }] {
+        let sheet = book.sheet(0).unwrap();
+        assert_eq!(sheet.value("A1"), "Namespace regression");
+        assert_eq!(sheet.value("B2"), "42");
+        assert!(sheet.style("A1").font().unwrap().bold());
+        assert_eq!(
+            sheet.style("A1").borders().unwrap().bottom().border_style(),
+            Border::BORDER_THIN
+        );
+    }
+}