diff --git a/lib/node_modules/@stdlib/array/uint64/README.md b/lib/node_modules/@stdlib/array/uint64/README.md
index 02da19409141..a223443cef20 100644
--- a/lib/node_modules/@stdlib/array/uint64/README.md
+++ b/lib/node_modules/@stdlib/array/uint64/README.md
@@ -335,6 +335,39 @@ var u = arr.get( 100 );
// returns undefined
```
+
+
+#### Uint64Array.prototype.lastIndexOf( searchElement\[, fromIndex] )
+
+Returns the last index at which a given element can be found.
+
+```javascript
+var Uint64 = require( '@stdlib/number/uint64/ctor' );
+
+var arr = new Uint64Array( [ 1, 2, 3, 4, 3 ] );
+
+var idx = arr.lastIndexOf( new Uint64( 3 ) );
+// returns 4
+
+idx = arr.lastIndexOf( 3, 3 );
+// returns 2
+
+idx = arr.lastIndexOf( 2, -3 );
+// returns 1
+```
+
+If `searchElement` is not present in the array, the method returns `-1`.
+
+```javascript
+var arr = new Uint64Array( [ 1, 2 ] );
+
+var idx = arr.lastIndexOf( 3 );
+// returns -1
+
+idx = arr.lastIndexOf( 2, 0 );
+// returns -1
+```
+
#### Uint64Array.prototype.set( value\[, i] )
diff --git a/lib/node_modules/@stdlib/array/uint64/benchmark/benchmark.last_index_of.js b/lib/node_modules/@stdlib/array/uint64/benchmark/benchmark.last_index_of.js
new file mode 100644
index 000000000000..8f97527581e8
--- /dev/null
+++ b/lib/node_modules/@stdlib/array/uint64/benchmark/benchmark.last_index_of.js
@@ -0,0 +1,52 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var bench = require( '@stdlib/bench' );
+var format = require( '@stdlib/string/format' );
+var pkg = require( './../package.json' ).name;
+var Uint64Array = require( './../lib' );
+
+
+// MAIN //
+
+bench( format( '%s:lastIndexOf', pkg ), function benchmark( b ) {
+ var out;
+ var arr;
+ var i;
+
+ arr = new Uint64Array( 10 );
+
+ // Benchmark worst case scenario (i.e., the search element is never present, so the method must scan the entire array)...
+ b.tic();
+ for ( i = 0; i < b.iterations; i++ ) {
+ out = arr.lastIndexOf( i+1 );
+ if ( out !== -1 ) {
+ b.fail( 'should return -1' );
+ }
+ }
+ b.toc();
+ if ( out !== -1 ) {
+ b.fail( 'should return -1' );
+ }
+ b.pass( 'benchmark finished' );
+ b.end();
+});
diff --git a/lib/node_modules/@stdlib/array/uint64/benchmark/benchmark.last_index_of.length.js b/lib/node_modules/@stdlib/array/uint64/benchmark/benchmark.last_index_of.length.js
new file mode 100644
index 000000000000..15a8167d6183
--- /dev/null
+++ b/lib/node_modules/@stdlib/array/uint64/benchmark/benchmark.last_index_of.length.js
@@ -0,0 +1,95 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var bench = require( '@stdlib/bench' );
+var pow = require( '@stdlib/math/base/special/pow' );
+var format = require( '@stdlib/string/format' );
+var pkg = require( './../package.json' ).name;
+var Uint64Array = require( './../lib' );
+
+
+// FUNCTIONS //
+
+/**
+* Creates a benchmark function.
+*
+* @private
+* @param {PositiveInteger} len - array length
+* @returns {Function} benchmark function
+*/
+function createBenchmark( len ) {
+ var arr = new Uint64Array( len );
+ return benchmark;
+
+ /**
+ * Benchmark function.
+ *
+ * @private
+ * @param {Benchmark} b - benchmark instance
+ */
+ function benchmark( b ) {
+ var out;
+ var i;
+
+ // Benchmark worst case scenario (i.e., the search element is never present, so the method must scan the entire array)...
+ b.tic();
+ for ( i = 0; i < b.iterations; i++ ) {
+ out = arr.lastIndexOf( i+1 );
+ if ( out !== -1 ) {
+ b.fail( 'should return -1' );
+ }
+ }
+ b.toc();
+ if ( out !== -1 ) {
+ b.fail( 'should return -1' );
+ }
+ b.pass( 'benchmark finished' );
+ b.end();
+ }
+}
+
+
+// MAIN //
+
+/**
+* Main execution sequence.
+*
+* @private
+*/
+function main() {
+ var len;
+ var min;
+ var max;
+ var f;
+ var i;
+
+ min = 1; // 10^min
+ max = 6; // 10^max
+
+ for ( i = min; i <= max; i++ ) {
+ len = pow( 10, i );
+ f = createBenchmark( len );
+ bench( format( '%s:lastIndexOf:len=%d', pkg, len ), f );
+ }
+}
+
+main();
diff --git a/lib/node_modules/@stdlib/array/uint64/docs/repl.txt b/lib/node_modules/@stdlib/array/uint64/docs/repl.txt
index c737fc5bf588..94db281dc782 100644
--- a/lib/node_modules/@stdlib/array/uint64/docs/repl.txt
+++ b/lib/node_modules/@stdlib/array/uint64/docs/repl.txt
@@ -299,6 +299,36 @@
[ 2n ]
+{{alias}}.prototype.lastIndexOf( searchElement[, fromIndex] )
+ Returns the last index at which a given element can be found.
+
+ If method does not find a search element, the method returns `-1`.
+
+ Parameters
+ ----------
+ searchElement: Uint64|number|bigint
+ Search element.
+
+ fromIndex: integer (optional)
+ Array index at which to start the search backward. If provided a
+ negative value, the method resolves the start index relative to the
+ last array element. Default: -1.
+
+ Returns
+ -------
+ out: integer
+ Array index or `-1`.
+
+ Examples
+ --------
+ > var arr = new {{alias}}( [ 1, 2, 3, 2 ] )
+ [ 1n, 2n, 3n, 2n ]
+ > var idx = arr.lastIndexOf( new {{alias:@stdlib/number/uint64/ctor}}( 2 ) )
+ 3
+ > idx = arr.lastIndexOf( 2, 2 )
+ 1
+
+
{{alias}}.prototype.set( v[, i] )
Sets one or more array elements.
diff --git a/lib/node_modules/@stdlib/array/uint64/docs/types/index.d.ts b/lib/node_modules/@stdlib/array/uint64/docs/types/index.d.ts
index 78b11c503625..47be3fc75401 100644
--- a/lib/node_modules/@stdlib/array/uint64/docs/types/index.d.ts
+++ b/lib/node_modules/@stdlib/array/uint64/docs/types/index.d.ts
@@ -477,6 +477,32 @@ declare class Uint64Array implements Uint64ArrayInterface {
*/
get( i: number ): Uint64 | void;
+ /**
+ * Returns the last index at which a given element can be found.
+ *
+ * @param searchElement - element to find
+ * @param fromIndex - index at which to start searching backward (inclusive)
+ * @returns index or -1
+ *
+ * @example
+ * var Uint64 = require( '@stdlib/number/uint64/ctor' );
+ *
+ * var arr = new Uint64Array( [ 1, 2, 3, 4, 3 ] );
+ *
+ * var idx = arr.lastIndexOf( new Uint64( 3 ) );
+ * // returns 4
+ *
+ * idx = arr.lastIndexOf( 3, 3 );
+ * // returns 2
+ *
+ * idx = arr.lastIndexOf( 5, 3 );
+ * // returns -1
+ *
+ * idx = arr.lastIndexOf( 2n, -3 );
+ * // returns 1
+ */
+ lastIndexOf( searchElement: Uint, fromIndex?: number ): number;
+
/**
* Sets an array element.
*
diff --git a/lib/node_modules/@stdlib/array/uint64/lib/main.js b/lib/node_modules/@stdlib/array/uint64/lib/main.js
index 684cb8e4b9bd..b48684cbaec1 100644
--- a/lib/node_modules/@stdlib/array/uint64/lib/main.js
+++ b/lib/node_modules/@stdlib/array/uint64/lib/main.js
@@ -740,6 +740,75 @@ setReadOnly( Uint64Array.prototype, 'get', function get( idx ) {
return getUint64( this._buffer, idx );
});
+/**
+* Returns the last index at which a given element can be found.
+*
+* @name lastIndexOf
+* @memberof Uint64Array.prototype
+* @type {Function}
+* @param {(Uint64|bigint|number)} searchElement - element to find
+* @param {integer} [fromIndex] - index at which to start searching backward (inclusive)
+* @throws {TypeError} `this` must be a 64-bit unsigned integer array
+* @throws {TypeError} first argument must be either a 64-bit unsigned integer or a value which can be converted to a 64-bit unsigned integer
+* @throws {TypeError} second argument must be an integer
+* @returns {integer} index or -1
+*
+* @example
+* var Uint64 = require( '@stdlib/number/uint64/ctor' );
+*
+* var arr = new Uint64Array( [ 1, 2, 3, 4, 3 ] );
+*
+* var idx = arr.lastIndexOf( new Uint64( 3 ) );
+* // returns 4
+*
+* idx = arr.lastIndexOf( 3, 3 );
+* // returns 2
+*
+* idx = arr.lastIndexOf( 5, 3 );
+* // returns -1
+*
+* idx = arr.lastIndexOf( 2n, -3 );
+* // returns 1
+*/
+setReadOnly( Uint64Array.prototype, 'lastIndexOf', function lastIndexOf( searchElement, fromIndex ) {
+ var words;
+ var buf;
+ var idx;
+ var i;
+ if ( !isUint64Array( this ) ) {
+ throw new TypeError( 'invalid invocation. `this` is not a 64-bit unsigned integer array.' );
+ }
+ if ( !isUint64( searchElement ) ) {
+ try {
+ searchElement = new Uint64( searchElement );
+ } catch ( err ) { // eslint-disable-line no-unused-vars
+ throw new TypeError( format( 'invalid argument. First argument must be either a 64-bit unsigned integer or a value which can be converted to a 64-bit unsigned integer. Value: `%s`.', searchElement ) );
+ }
+ }
+ if ( arguments.length > 1 ) {
+ if ( !isIntegerPrimitive( fromIndex ) ) {
+ throw new TypeError( format( 'invalid argument. Second argument must be an integer. Value: `%s`.', fromIndex ) );
+ }
+ if ( fromIndex >= this._length ) {
+ fromIndex = this._length - 1;
+ } else if ( fromIndex < 0 ) {
+ fromIndex += this._length;
+ }
+ } else {
+ fromIndex = this._length - 1;
+ }
+ words = [ 0, 0 ];
+ toWords( searchElement, words, 1, 0 );
+ buf = this._buffer;
+ for ( i = fromIndex; i >= 0; i-- ) {
+ idx = 2 * i;
+ if ( words[ 0 ] === buf[ idx+indices.HIGH ] && words[ 1 ] === buf[ idx+indices.LOW ] ) { // eslint-disable-line max-len
+ return i;
+ }
+ }
+ return -1;
+});
+
/**
* Number of array elements.
*
diff --git a/lib/node_modules/@stdlib/array/uint64/test/test.last_index_of.js b/lib/node_modules/@stdlib/array/uint64/test/test.last_index_of.js
new file mode 100644
index 000000000000..a34a4d837f9d
--- /dev/null
+++ b/lib/node_modules/@stdlib/array/uint64/test/test.last_index_of.js
@@ -0,0 +1,251 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var tape = require( 'tape' );
+var hasOwnProp = require( '@stdlib/assert/has-own-property' );
+var hasBigIntSupport = require( '@stdlib/assert/has-bigint-support' );
+var isFunction = require( '@stdlib/assert/is-function' );
+var BigInt = require( '@stdlib/bigint/ctor' );
+var Uint64 = require( '@stdlib/number/uint64/ctor' );
+var Uint64Array = require( './../lib' );
+
+
+// VARIABLES //
+
+var HAS_BIGINTS = hasBigIntSupport();
+var opts = {
+ 'skip': !HAS_BIGINTS
+};
+
+
+// TESTS //
+
+tape( 'main export is a function', function test( t ) {
+ t.ok( true, __filename );
+ t.strictEqual( typeof Uint64Array, 'function', 'main export is a function' );
+ t.end();
+});
+
+tape( 'attached to the prototype of the main export is a `lastIndexOf` method', function test( t ) {
+ t.strictEqual( hasOwnProp( Uint64Array.prototype, 'lastIndexOf' ), true, 'has property' );
+ t.strictEqual( isFunction( Uint64Array.prototype.lastIndexOf ), true, 'has method' );
+ t.end();
+});
+
+tape( 'the method throws an error if invoked with a `this` context which is not a 64-bit unsigned integer array instance', function test( t ) {
+ var values;
+ var arr;
+ var i;
+
+ arr = new Uint64Array( 5 );
+
+ values = [
+ '5',
+ 5,
+ NaN,
+ true,
+ false,
+ null,
+ void 0,
+ {},
+ []
+ ];
+ for ( i = 0; i < values.length; i++ ) {
+ t.throws( badValue( values[i] ), TypeError, 'throws an error when provided '+values[i] );
+ }
+ t.end();
+
+ function badValue( value ) {
+ return function badValue() {
+ return arr.lastIndexOf.call( value, new Uint64( 1 ) );
+ };
+ }
+});
+
+tape( 'the method throws an error if provided a first argument which is not either a 64-bit unsigned integer or a value which can be converted to a 64-bit unsigned integer', function test( t ) {
+ var values;
+ var arr;
+ var i;
+
+ arr = new Uint64Array( 5 );
+
+ values = [
+ '5',
+ 3.14,
+ -5,
+ NaN,
+ true,
+ false,
+ null,
+ void 0,
+ {},
+ [],
+ function noop() {}
+ ];
+ for ( i = 0; i < values.length; i++ ) {
+ t.throws( badValue( values[i] ), TypeError, 'throws an error when provided '+values[i] );
+ }
+ t.end();
+
+ function badValue( value ) {
+ return function badValue() {
+ return arr.lastIndexOf( value );
+ };
+ }
+});
+
+tape( 'the method throws an error if provided a second argument which is not an integer', function test( t ) {
+ var values;
+ var arr;
+ var i;
+
+ arr = new Uint64Array( 10 );
+
+ values = [
+ '5',
+ 3.14,
+ NaN,
+ true,
+ false,
+ null,
+ void 0,
+ {},
+ [],
+ function noop() {}
+ ];
+ for ( i = 0; i < values.length; i++ ) {
+ t.throws( badValue( values[i] ), TypeError, 'throws an error when provided '+values[i] );
+ }
+ t.end();
+
+ function badValue( value ) {
+ return function badValue() {
+ return arr.lastIndexOf( new Uint64( 1 ), value );
+ };
+ }
+});
+
+tape( 'the method returns `-1` if operating on an empty 64-bit unsigned integer array', function test( t ) {
+ var arr;
+ var idx;
+
+ arr = new Uint64Array();
+ idx = arr.lastIndexOf( new Uint64( 1 ) );
+
+ t.strictEqual( idx, -1, 'returns expected value' );
+ t.end();
+});
+
+tape( 'the method returns `-1` if a 64-bit unsigned integer is not found', function test( t ) {
+ var arr;
+ var idx;
+
+ arr = new Uint64Array( 10 );
+ idx = arr.lastIndexOf( new Uint64( 1 ) );
+
+ t.strictEqual( idx, -1, 'returns expected value' );
+ t.end();
+});
+
+tape( 'the method returns the index of the first match when searching from the end of the array if a search element is found', function test( t ) {
+ var arr;
+ var idx;
+
+ arr = new Uint64Array( [ 1, 2, 3, 2 ] );
+ idx = arr.lastIndexOf( new Uint64( 2 ) );
+
+ t.strictEqual( idx, 3, 'returns expected value' );
+ t.end();
+});
+
+tape( 'the method supports providing a search element which is a nonnegative integer', function test( t ) {
+ var arr;
+ var idx;
+
+ arr = new Uint64Array( [ 1, 2, 3, 2 ] );
+
+ idx = arr.lastIndexOf( 2 );
+ t.strictEqual( idx, 3, 'returns expected value' );
+
+ idx = arr.lastIndexOf( 4 );
+ t.strictEqual( idx, -1, 'returns expected value' );
+ t.end();
+});
+
+tape( 'the method supports providing a search element which is a bigint', opts, function test( t ) {
+ var arr;
+ var idx;
+
+ arr = new Uint64Array( [ 1, 2, 3, 2 ] );
+
+ idx = arr.lastIndexOf( BigInt( 2 ) );
+ t.strictEqual( idx, 3, 'returns expected value' );
+
+ idx = arr.lastIndexOf( BigInt( 4 ) );
+ t.strictEqual( idx, -1, 'returns expected value' );
+ t.end();
+});
+
+tape( 'the method supports specifying a starting search index', function test( t ) {
+ var arr;
+ var idx;
+
+ arr = new Uint64Array( [ 1, 2, 3, 2, 3 ] );
+
+ idx = arr.lastIndexOf( new Uint64( 2 ), 4 );
+ t.strictEqual( idx, 3, 'returns expected value' );
+
+ idx = arr.lastIndexOf( new Uint64( 2 ), 2 );
+ t.strictEqual( idx, 1, 'returns expected value' );
+
+ idx = arr.lastIndexOf( new Uint64( 3 ), 1 );
+ t.strictEqual( idx, -1, 'returns expected value' );
+ t.end();
+});
+
+tape( 'the method supports specifying a starting search index (negative)', function test( t ) {
+ var arr;
+ var idx;
+
+ arr = new Uint64Array( [ 1, 2, 3, 2, 2 ] );
+
+ idx = arr.lastIndexOf( new Uint64( 2 ), -3 );
+ t.strictEqual( idx, 1, 'returns expected value' );
+
+ idx = arr.lastIndexOf( new Uint64( 3 ), -1 );
+ t.strictEqual( idx, 2, 'returns expected value' );
+ t.end();
+});
+
+tape( 'when the method is provided a starting index which resolves to an index which exceeds the maximum array index, the method searches from the last array element', function test( t ) {
+ var arr;
+ var idx;
+
+ arr = new Uint64Array( [ 1, 2, 3, 2, 2 ] );
+
+ idx = arr.lastIndexOf( new Uint64( 2 ), 10 );
+ t.strictEqual( idx, 4, 'returns expected value' );
+
+ idx = arr.lastIndexOf( new Uint64( 4 ), 10 );
+ t.strictEqual( idx, -1, 'returns expected value' );
+ t.end();
+});