diff --git a/src/Collections/IComparable.php b/src/Collections/IComparable.php
new file mode 100644
index 0000000..33ba7b8
--- /dev/null
+++ b/src/Collections/IComparable.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace jrosset\Collections;
+
+/**
+ * Interface for comparable objects
+ *
+ * @template TObject of object
+ */
+interface IComparable {
+    /**
+     * Compare to another instance
+     *
+     * @param TObject $other The other instance
+     *
+     * @return int <br>&lt; 0 if current instance is classed before the other instance
+     *             <br>= 0 if current instance is classed equals the other instance
+     *             <br>&gt; 0 if current instance is classed after the other instance
+     *
+     * @noinspection PhpMissingParamTypeInspection
+     */
+    public function compareTo ($other): int;
+}
\ No newline at end of file
diff --git a/src/Collections/IComparator.php b/src/Collections/IComparator.php
new file mode 100644
index 0000000..c63e67e
--- /dev/null
+++ b/src/Collections/IComparator.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace jrosset\Collections;
+
+/**
+ * Interface for classes comparing external objects
+ *
+ * @template TObject of object
+ */
+interface IComparator {
+    /**
+     * Compare two objects
+     *
+     * @param TObject $object1 The first object
+     * @param TObject $object2 The second object
+     *
+     * @return int <br>&lt; 0 if the first object is classed before the second object
+     *             <br>= 0 if the first object is classed equals the second object
+     *             <br>&gt; 0 if the first object is classed after the second object
+     *
+     * @noinspection PhpMissingParamTypeInspection
+     */
+    public function compare ($object1, $object2): int;
+}
\ No newline at end of file
diff --git a/src/Collections/IImmutableCollection.php b/src/Collections/IImmutableCollection.php
index 45a74ea..9c03f17 100644
--- a/src/Collections/IImmutableCollection.php
+++ b/src/Collections/IImmutableCollection.php
@@ -8,6 +8,7 @@ use Countable;
 use IteratorAggregate;
 use JsonSerializable;
 use Serializable;
+use Throwable;
 
 /**
  * Interface for an immutable (read-only) collection
@@ -126,6 +127,40 @@ interface IImmutableCollection extends IteratorAggregate, JsonSerializable, Seri
      */
     public function map (Closure $process): self;
 
+    /**
+     * Sort the elements (by value)
+     *
+     * @param null|IComparator|Closure(TValue, TValue):int $sorter The sorting method ; Null if values are object implementing {@see IComparable}.
+     *                                                             <br>Return :
+     *                                                             <br>&lt; 0 if value1 is before value2
+     *                                                             <br>= 0 if value1 equals value2
+     *                                                             <br>&gt; 0 if value1 is after value2
+     *
+     * @return static The sorted collection
+     * @psalm-return static<TKey, TValue>
+     *
+     * @throws Throwable If an error occurs
+     *
+     * @noinspection PhpMissingReturnTypeInspection
+     */
+    public function sort ($sorter = null);
+    /**
+     * Sort the elements by key
+     *
+     * @param IComparator|Closure(TKey, TKey):int $sorter The sorting method. Return :
+     *                                                    <br>&lt; 0 if key1 is before key2
+     *                                                    <br>= 0 if key1 equals key2
+     *                                                    <br>&gt; 0 if key1 is after key2
+     *
+     * @return static The sorted collection
+     * @psalm-return static<TKey, TValue>
+     *
+     * @throws Throwable If an error occurs
+     *
+     * @noinspection PhpMissingReturnTypeInspection
+     */
+    public function sortByKey ($sorter);
+
     /**
      * The list of all keys
      *
diff --git a/src/Collections/ImmutableCollection.php b/src/Collections/ImmutableCollection.php
index e358d87..74d636d 100644
--- a/src/Collections/ImmutableCollection.php
+++ b/src/Collections/ImmutableCollection.php
@@ -294,6 +294,42 @@ class ImmutableCollection implements IImmutableCollection {
         return $output;
     }
 
+    /**
+     * @inheritDoc
+     */
+    public function sort ($sorter = null) {
+        if ($sorter === null) {
+            $sorter = function (IComparable $value1, IComparable $value2): int {
+                return $value1->compareTo($value2);
+            };
+        }
+        elseif ($sorter instanceof IComparator) {
+            $sorter = function ($value1, $value2) use ($sorter): int {
+                return $sorter->compare($value1, $value2);
+            };
+        }
+
+        $elements = $this->toArray();
+        uasort($elements, $sorter);
+
+        return new static($elements);
+    }
+    /**
+     * @inheritDoc
+     */
+    public function sortByKey ($sorter) {
+        if ($sorter instanceof IComparator) {
+            $sorter = function ($value1, $value2) use ($sorter): int {
+                return $sorter->compare($value1, $value2);
+            };
+        }
+
+        $elements = $this->toArray();
+        uksort($elements, $sorter);
+
+        return new static($elements);
+    }
+
     /**
      * @inheritDoc
      */
diff --git a/tests/test_class.php b/tests/test_class.php
index 77cbd71..837f4db 100644
--- a/tests/test_class.php
+++ b/tests/test_class.php
@@ -1,11 +1,19 @@
 <?php
+/** @noinspection PhpUnhandledExceptionInspection */
 /** @noinspection PhpIllegalPsrClassPathInspection */
 
 use jrosset\Collections\Collection;
+use jrosset\Collections\IComparable;
+use jrosset\Collections\IComparator;
 
 require_once __DIR__ . '/../vendor/autoload.php';
 
-class Measure {
+/**
+ * Class Measure
+ *
+ * @implements IComparable<static>
+ */
+class Measure implements IComparable {
     private int    $value;
     private string $unit;
 
@@ -14,9 +22,33 @@ class Measure {
         $this->unit = $unit;
     }
 
+    public function getValue (): int {
+        return $this->value;
+    }
+
     public function asString (): string {
         return $this->value . $this->unit;
     }
+
+    /**
+     * @inheritDoc
+     */
+    public function compareTo ($other): int {
+        return $this->value <=> $other->value;
+    }
+}
+/**
+ * Class MeasureReverseComparator
+ *
+ * @implements IComparator<Measure>
+ */
+class MeasureReverseComparator implements IComparator {
+    /**
+     * @inheritDoc
+     */
+    public function compare ($object1, $object2): int {
+        return -($object1->getValue() <=> $object2->getValue());
+    }
 }
 
 /**
@@ -34,6 +66,11 @@ function getMeasures (): Collection {
 }
 
 echo 'Measures :' . PHP_EOL;
-foreach (getMeasures() as $no => $measure) {
+foreach (getMeasures()->sort() as $no => $measure) {
+    echo "\t#" . $no . ' = ' . $measure->asString() . PHP_EOL;
+}
+
+echo 'Measures (reversed) :' . PHP_EOL;
+foreach (getMeasures()->sort(new MeasureReverseComparator()) as $no => $measure) {
     echo "\t#" . $no . ' = ' . $measure->asString() . PHP_EOL;
 }
\ No newline at end of file