diff --git a/src/lib/es2020.intl.d.ts b/src/lib/es2020.intl.d.ts
index 5ab347994647e..7b3560a4d7dfd 100644
--- a/src/lib/es2020.intl.d.ts
+++ b/src/lib/es2020.intl.d.ts
@@ -451,6 +451,6 @@ declare namespace Intl {
         new (locales?: LocalesArgument, options?: PluralRulesOptions): PluralRules;
         (locales?: LocalesArgument, options?: PluralRulesOptions): PluralRules;
 
-        supportedLocalesOf(locales: LocalesArgument, options?: { localeMatcher?: "lookup" | "best fit"; }): string[];
+        supportedLocalesOf(locales: LocalesArgument, options?: { localeMatcher?: RelativeTimeFormatLocaleMatcher; }): string[];
     }
 }
diff --git a/src/lib/esnext.intl.d.ts b/src/lib/esnext.intl.d.ts
index 9aacedd724469..4ef282c90a305 100644
--- a/src/lib/esnext.intl.d.ts
+++ b/src/lib/esnext.intl.d.ts
@@ -1,3 +1,168 @@
 declare namespace Intl {
-    // Empty
+    type DurationTimeFormatLocaleMatcher = "lookup" | "best fit";
+    /**
+     * Value of the `unit` property in duration objects
+     *
+     * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DurationFormat/format#duration).
+     */
+    type DurationTimeFormatUnit = "years"|"months"|"weeks"|"days"|"hours"|"minutes"|"seconds"|"milliseconds"|"microseconds"|"nanoseconds"
+    
+    /**
+     * The style of the formatted duration.
+     *
+     * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DurationFormat/DurationFormat#style).
+     */
+    type DurationFormatStyle = "long" | "short" | "narrow" | "digital"
+
+    
+    type DurationFormatUnitSingular =
+    | "year"
+    | "quarter"
+    | "month"
+    | "week"
+    | "day"
+    | "hour"
+    | "minute"
+    | "second";
+
+    /**
+     * An object representing the relative time format in parts
+     * that can be used for custom locale-aware formatting.
+     *
+     * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DurationFormat/formatToParts#examples).
+     */
+        type DurationFormatPart =
+        | {
+            type: "literal";
+            value: string;
+        }
+        | {
+            type: Exclude<NumberFormatPartTypes, "literal">;
+            value: string;
+            unit: DurationFormatUnitSingular;
+        };
+
+
+
+    type DurationFormatOption = "long"|"short"|"narrow"|"numeric"|"2-digit"
+
+
+    type DurationFormatDisplayOption = "always"|"auto";    
+
+    /**
+     * Number of how many fractional second digits to display in the output.
+     *
+     * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DurationFormat/DurationFormat#fractionaldigits).
+     */
+    type fractionalDigitsOption = 0|1|2|3|4|5|6|7|8|9
+
+    interface ResolvedDurationFormatOptions {
+        locale?: UnicodeBCP47LocaleIdentifier
+        numberingSystem?: DateTimeFormatOptions["numberingSystem"]
+        style?: DurationFormatStyle
+        years?: Omit<DurationFormatOptions,"numeric"|"2-digit">
+        yearsDisplay?:DurationFormatDisplayOption
+        months?: Omit<DurationFormatOptions,"numeric"|"2-digit">
+        monthsDisplay?: DurationFormatDisplayOption
+        weeks?: Omit<DurationFormatOptions,"numeric"|"2-digit">
+        weeksDisplay?: DurationFormatDisplayOption
+        days?: Omit<DurationFormatOptions,"numeric"|"2-digit">
+        daysDisplay?: DurationFormatDisplayOption
+        hours?: DurationFormatOptions
+        hoursDisplay?: DurationFormatDisplayOption
+        minutes?: DurationFormatOptions
+        minutesDisplay?: DurationFormatDisplayOption
+        seconds?: DurationFormatOptions
+        secondsDisplay?: DurationFormatDisplayOption
+        milliseconds?: DurationFormatOptions
+        millisecondsDisplay?: DurationFormatDisplayOption
+        microseconds?: DurationFormatOptions
+        microsecondsDisplay?: DurationFormatDisplayOption
+        nanosecond?: DurationFormatOptions
+        nanosecondDisplay?: DurationFormatDisplayOption
+        fractionalDigits?: fractionalDigitsOption
+    }
+
+    interface DurationFormatOptions {
+        localeMatcher?: DurationTimeFormatLocaleMatcher
+        numberingSystem?: DateTimeFormatOptions["numberingSystem"]
+        style?: DurationFormatStyle
+        years?: Omit<DurationFormatOption,"numeric"|"2-digit">
+        yearsDisplay?:DurationFormatDisplayOption
+        months?: Omit<DurationFormatOption,"numeric"|"2-digit">
+        monthsDisplay?: DurationFormatDisplayOption
+        weeks?: Omit<DurationFormatOption,"numeric"|"2-digit">
+        weeksDisplay?: DurationFormatDisplayOption
+        days?: Omit<DurationFormatOption,"numeric"|"2-digit">
+        daysDisplay?: DurationFormatDisplayOption
+        hours?: DurationFormatOption
+        hoursDisplay?: DurationFormatDisplayOption
+        minutes?: DurationFormatOption
+        minutesDisplay?: DurationFormatDisplayOption
+        seconds?: DurationFormatOption
+        secondsDisplay?: DurationFormatDisplayOption
+        milliseconds?: DurationFormatOption
+        millisecondsDisplay?: DurationFormatDisplayOption
+        microseconds?: DurationFormatOption
+        microsecondsDisplay?: DurationFormatDisplayOption
+        nanosecond?: DurationFormatOption
+        nanosecondDisplay?: DurationFormatDisplayOption
+        fractionalDigits?: fractionalDigitsOption
+    }
+
+    /**
+     * The duration object to be formatted
+     * 
+     * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DurationFormat/format#duration).
+     */
+    type DurationType = Record<DurationTimeFormatUnit,number>
+
+    interface DurationFormat {
+        /**
+         * @param duration The duration object to be formatted. It should include some or all of the following properties: months, weeks, days, hours, minutes, seconds, milliseconds, microseconds, nanoseconds.
+         * 
+         * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DurationFormat/format).
+         */
+        format(duration: DurationType): string;
+        /**
+         * @param duration The duration object to be formatted. It should include some or all of the following properties: months, weeks, days, hours, minutes, seconds, milliseconds, microseconds, nanoseconds.
+         *
+         * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DurationFormat/formatToParts).
+         */
+        formatToParts(duration: DurationType): DurationFormatPart[];
+        /**
+         * [MDN](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Intl/DurationFormat/resolvedOptions).
+         */
+        resolvedOptions(): ResolvedDurationFormatOptions;
+    }
+
+    const DurationFormat: {
+        prototype: DurationFormat;
+
+        /**
+         * @param locales A string with a BCP 47 language tag, or an array of such strings.
+         *   For the general form and interpretation of the `locales` argument, see the [Intl](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Intl#locale_identification_and_negotiation)
+         *   page.
+         *
+         * @param options An object for setting up a duration format.
+         *
+         * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DurationFormat/DurationFormat).
+         */
+        new (locales: LocalesArgument, options: DurationFormatOptions): DurationFormat;
+
+        /**
+         * Returns an array containing those of the provided locales that are supported in display names without having to fall back to the runtime's default locale.
+         *
+         * @param locales A string with a BCP 47 language tag, or an array of such strings.
+         *   For the general form and interpretation of the `locales` argument, see the [Intl](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Intl#locale_identification_and_negotiation)
+         *   page.
+         *
+         * @param options An object with a locale matcher.
+         *
+         * @returns An array of strings representing a subset of the given locale tags that are supported in display names without having to fall back to the runtime's default locale.
+         *
+         * [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DurationFormat/supportedLocalesOf).
+         */
+        supportedLocalesOf(locales?: LocalesArgument, options?: { localeMatcher?: DurationTimeFormatLocaleMatcher; }): UnicodeBCP47LocaleIdentifier[];
+    };
 }