diff --git a/Libraries/LibWeb/CMakeLists.txt b/Libraries/LibWeb/CMakeLists.txt
index 2a3e0c70436..45c38a900ef 100644
--- a/Libraries/LibWeb/CMakeLists.txt
+++ b/Libraries/LibWeb/CMakeLists.txt
@@ -164,6 +164,7 @@ set(SOURCES
     CSS/StyleValues/EasingStyleValue.cpp
     CSS/StyleValues/EdgeStyleValue.cpp
     CSS/StyleValues/FilterValueListStyleValue.cpp
+    CSS/StyleValues/FontSourceStyleValue.cpp
     CSS/StyleValues/GridAutoFlowStyleValue.cpp
     CSS/StyleValues/GridTemplateAreaStyleValue.cpp
     CSS/StyleValues/GridTrackPlacementStyleValue.cpp
diff --git a/Libraries/LibWeb/CSS/CSSStyleValue.cpp b/Libraries/LibWeb/CSS/CSSStyleValue.cpp
index 6ba2ac82cfe..03b2886070b 100644
--- a/Libraries/LibWeb/CSS/CSSStyleValue.cpp
+++ b/Libraries/LibWeb/CSS/CSSStyleValue.cpp
@@ -33,6 +33,7 @@
 #include <LibWeb/CSS/StyleValues/FilterValueListStyleValue.h>
 #include <LibWeb/CSS/StyleValues/FitContentStyleValue.h>
 #include <LibWeb/CSS/StyleValues/FlexStyleValue.h>
+#include <LibWeb/CSS/StyleValues/FontSourceStyleValue.h>
 #include <LibWeb/CSS/StyleValues/FrequencyStyleValue.h>
 #include <LibWeb/CSS/StyleValues/GridAutoFlowStyleValue.h>
 #include <LibWeb/CSS/StyleValues/GridTemplateAreaStyleValue.h>
@@ -196,6 +197,12 @@ FlexStyleValue const& CSSStyleValue::as_flex() const
     return static_cast<FlexStyleValue const&>(*this);
 }
 
+FontSourceStyleValue const& CSSStyleValue::as_font_source() const
+{
+    VERIFY(is_font_source());
+    return static_cast<FontSourceStyleValue const&>(*this);
+}
+
 FrequencyStyleValue const& CSSStyleValue::as_frequency() const
 {
     VERIFY(is_frequency());
diff --git a/Libraries/LibWeb/CSS/CSSStyleValue.h b/Libraries/LibWeb/CSS/CSSStyleValue.h
index 0fd3a50dd14..bc7ab385e6a 100644
--- a/Libraries/LibWeb/CSS/CSSStyleValue.h
+++ b/Libraries/LibWeb/CSS/CSSStyleValue.h
@@ -106,6 +106,7 @@ public:
         FilterValueList,
         FitContent,
         Flex,
+        FontSource,
         FontVariant,
         Frequency,
         GridAutoFlow,
@@ -228,6 +229,10 @@ public:
     FlexStyleValue const& as_flex() const;
     FlexStyleValue& as_flex() { return const_cast<FlexStyleValue&>(const_cast<CSSStyleValue const&>(*this).as_flex()); }
 
+    bool is_font_source() const { return type() == Type::FontSource; }
+    FontSourceStyleValue const& as_font_source() const;
+    FontSourceStyleValue& as_font_source() { return const_cast<FontSourceStyleValue&>(const_cast<CSSStyleValue const&>(*this).as_font_source()); }
+
     bool is_frequency() const { return type() == Type::Frequency; }
     FrequencyStyleValue const& as_frequency() const;
     FrequencyStyleValue& as_frequency() { return const_cast<FrequencyStyleValue&>(const_cast<CSSStyleValue const&>(*this).as_frequency()); }
diff --git a/Libraries/LibWeb/CSS/Parser/Parser.h b/Libraries/LibWeb/CSS/Parser/Parser.h
index 15dc7b06fdf..765a3e38fcb 100644
--- a/Libraries/LibWeb/CSS/Parser/Parser.h
+++ b/Libraries/LibWeb/CSS/Parser/Parser.h
@@ -341,6 +341,7 @@ private:
     RefPtr<PositionStyleValue> parse_position_value(TokenStream<ComponentValue>&, PositionParsingMode = PositionParsingMode::Normal);
     RefPtr<CSSStyleValue> parse_filter_value_list_value(TokenStream<ComponentValue>&);
     RefPtr<StringStyleValue> parse_opentype_tag_value(TokenStream<ComponentValue>&);
+    RefPtr<FontSourceStyleValue> parse_font_source_value(TokenStream<ComponentValue>&);
 
     RefPtr<CSSStyleValue> parse_angle_value(TokenStream<ComponentValue>&);
     RefPtr<CSSStyleValue> parse_angle_percentage_value(TokenStream<ComponentValue>&);
diff --git a/Libraries/LibWeb/CSS/Parser/ValueParsing.cpp b/Libraries/LibWeb/CSS/Parser/ValueParsing.cpp
index 19446cde0ec..ddfd5903b14 100644
--- a/Libraries/LibWeb/CSS/Parser/ValueParsing.cpp
+++ b/Libraries/LibWeb/CSS/Parser/ValueParsing.cpp
@@ -16,6 +16,7 @@
 #include <AK/GenericLexer.h>
 #include <AK/TemporaryChange.h>
 #include <LibURL/URL.h>
+#include <LibWeb/CSS/FontFace.h>
 #include <LibWeb/CSS/Parser/Parser.h>
 #include <LibWeb/CSS/PropertyName.h>
 #include <LibWeb/CSS/StyleValues/AngleStyleValue.h>
@@ -39,6 +40,7 @@
 #include <LibWeb/CSS/StyleValues/EdgeStyleValue.h>
 #include <LibWeb/CSS/StyleValues/FitContentStyleValue.h>
 #include <LibWeb/CSS/StyleValues/FlexStyleValue.h>
+#include <LibWeb/CSS/StyleValues/FontSourceStyleValue.h>
 #include <LibWeb/CSS/StyleValues/FrequencyStyleValue.h>
 #include <LibWeb/CSS/StyleValues/GridTrackPlacementStyleValue.h>
 #include <LibWeb/CSS/StyleValues/GridTrackSizeListStyleValue.h>
@@ -3655,6 +3657,67 @@ RefPtr<StringStyleValue> Parser::parse_opentype_tag_value(TokenStream<ComponentV
     return string_value;
 }
 
+RefPtr<FontSourceStyleValue> Parser::parse_font_source_value(TokenStream<ComponentValue>& tokens)
+{
+    // <font-src> = <url> [ format(<font-format>)]? [ tech( <font-tech>#)]? | local(<family-name>)
+    auto transaction = tokens.begin_transaction();
+
+    tokens.discard_whitespace();
+
+    // local(<family-name>)
+    if (tokens.next_token().is_function("local"sv)) {
+        auto const& function = tokens.consume_a_token().function();
+        TokenStream function_tokens { function.value };
+        if (auto family_name = parse_family_name_value(function_tokens)) {
+            transaction.commit();
+            return FontSourceStyleValue::create(FontSourceStyleValue::Local { family_name.release_nonnull() }, {});
+        }
+        return nullptr;
+    }
+
+    // <url> [ format(<font-format>)]? [ tech( <font-tech>#)]?
+    auto url = parse_url_function(tokens);
+    if (!url.has_value() || !url->is_valid())
+        return nullptr;
+
+    Optional<FlyString> format;
+
+    tokens.discard_whitespace();
+
+    // [ format(<font-format>)]?
+    if (tokens.next_token().is_function("format"sv)) {
+        auto const& function = tokens.consume_a_token().function();
+        auto context_guard = push_temporary_value_parsing_context(FunctionContext { function.name });
+
+        TokenStream format_tokens { function.value };
+        format_tokens.discard_whitespace();
+        auto const& format_name_token = format_tokens.consume_a_token();
+        FlyString format_name;
+        if (format_name_token.is(Token::Type::Ident)) {
+            format_name = format_name_token.token().ident();
+        } else if (format_name_token.is(Token::Type::String)) {
+            format_name = format_name_token.token().string();
+        } else {
+            dbgln_if(CSS_PARSER_DEBUG, "CSSParser: font source invalid (`format()` parameter not an ident or string; is: {}); discarding.", format_name_token.to_debug_string());
+            return nullptr;
+        }
+
+        if (!font_format_is_supported(format_name)) {
+            dbgln_if(CSS_PARSER_DEBUG, "CSSParser: font source format({}) not supported; skipping.", format_name);
+            return nullptr;
+        }
+
+        format = move(format_name);
+    }
+
+    tokens.discard_whitespace();
+
+    // FIXME: [ tech( <font-tech>#)]?
+
+    transaction.commit();
+    return FontSourceStyleValue::create(url.release_value(), move(format));
+}
+
 NonnullRefPtr<CSSStyleValue> Parser::resolve_unresolved_style_value(ParsingParams const& context, DOM::Element& element, Optional<PseudoElement> pseudo_element, PropertyID property_id, UnresolvedStyleValue const& unresolved)
 {
     // Unresolved always contains a var() or attr(), unless it is a custom property's value, in which case we shouldn't be trying
diff --git a/Libraries/LibWeb/CSS/StyleValues/FontSourceStyleValue.cpp b/Libraries/LibWeb/CSS/StyleValues/FontSourceStyleValue.cpp
new file mode 100644
index 00000000000..644eb093443
--- /dev/null
+++ b/Libraries/LibWeb/CSS/StyleValues/FontSourceStyleValue.cpp
@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2025, Sam Atkins <sam@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/CSS/Serialize.h>
+#include <LibWeb/CSS/StyleValues/FontSourceStyleValue.h>
+
+namespace Web::CSS {
+
+FontSourceStyleValue::FontSourceStyleValue(Source source, Optional<FlyString> format)
+    : StyleValueWithDefaultOperators(Type::FontSource)
+    , m_source(move(source))
+    , m_format(move(format))
+{
+}
+
+FontSourceStyleValue::~FontSourceStyleValue() = default;
+
+String FontSourceStyleValue::to_string(SerializationMode) const
+{
+    // <font-src> = <url> [ format(<font-format>)]? [ tech( <font-tech>#)]? | local(<family-name>)
+    return m_source.visit(
+        [](Local const& local) {
+            // local(<family-name>)
+            StringBuilder builder;
+            serialize_a_local(builder, local.name->to_string(SerializationMode::Normal));
+            return builder.to_string_without_validation();
+        },
+        [this](URL::URL const& url) {
+            // <url> [ format(<font-format>)]? [ tech( <font-tech>#)]?
+            // FIXME: tech()
+            StringBuilder builder;
+            serialize_a_url(builder, url.to_string());
+
+            if (m_format.has_value()) {
+                builder.append(" format("sv);
+                serialize_an_identifier(builder, *m_format);
+                builder.append(")"sv);
+            }
+
+            return builder.to_string_without_validation();
+        });
+}
+
+bool FontSourceStyleValue::properties_equal(FontSourceStyleValue const& other) const
+{
+    bool sources_equal = m_source.visit(
+        [&other](Local const& local) {
+            if (auto* other_local = other.m_source.get_pointer<Local>()) {
+                return local.name == other_local->name;
+            }
+            return false;
+        },
+        [&other](URL::URL const& url) {
+            if (auto* other_url = other.m_source.get_pointer<URL::URL>()) {
+                return url == *other_url;
+            }
+            return false;
+        });
+
+    return sources_equal
+        && m_format == other.m_format;
+}
+
+}
diff --git a/Libraries/LibWeb/CSS/StyleValues/FontSourceStyleValue.h b/Libraries/LibWeb/CSS/StyleValues/FontSourceStyleValue.h
new file mode 100644
index 00000000000..732f990bdaa
--- /dev/null
+++ b/Libraries/LibWeb/CSS/StyleValues/FontSourceStyleValue.h
@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2025, Sam Atkins <sam@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/FlyString.h>
+#include <LibWeb/CSS/CSSStyleValue.h>
+
+namespace Web::CSS {
+
+class FontSourceStyleValue final : public StyleValueWithDefaultOperators<FontSourceStyleValue> {
+public:
+    struct Local {
+        NonnullRefPtr<CSSStyleValue> name;
+    };
+    using Source = Variant<Local, URL::URL>;
+
+    static ValueComparingNonnullRefPtr<FontSourceStyleValue> create(Source source, Optional<FlyString> format)
+    {
+        return adopt_ref(*new (nothrow) FontSourceStyleValue(move(source), move(format)));
+    }
+    virtual ~FontSourceStyleValue() override;
+
+    Source const& source() const { return m_source; }
+    Optional<FlyString> const& format() const { return m_format; }
+
+    virtual String to_string(SerializationMode) const override;
+
+    bool properties_equal(FontSourceStyleValue const&) const;
+
+private:
+    FontSourceStyleValue(Source source, Optional<FlyString> format);
+
+    Source m_source;
+    Optional<FlyString> m_format;
+};
+
+}
diff --git a/Libraries/LibWeb/Forward.h b/Libraries/LibWeb/Forward.h
index 5481b19c46c..378fc59c2c6 100644
--- a/Libraries/LibWeb/Forward.h
+++ b/Libraries/LibWeb/Forward.h
@@ -198,6 +198,7 @@ class FlexOrCalculated;
 class FlexStyleValue;
 class FontFace;
 class FontFaceSet;
+class FontSourceStyleValue;
 class Frequency;
 class FrequencyOrCalculated;
 class FrequencyPercentage;