diff --git a/Validate.php b/Validate.php
index 16aa700..868b8d7 100644
--- a/Validate.php
+++ b/Validate.php
@@ -101,4 +101,55 @@ class Validate
         return ($value >= $min && $value <= $max);
     }
 
+    /**
+     * Static function for validating a IBAN (International Bank Account Number).
+     * @param string $iban International Bank Account Number
+     * @return bool is the IBAN valid?
+     */
+    static function iban(string $iban) : bool
+    {
+        $country_length = [
+            "AL" => 28, "AD" => 24, "AT" => 20, "AZ" => 28, "BH" => 22, "BE" => 16, "BA" => 20, "BR" => 29, "BG" => 22, "CR" => 21,
+            "HR" => 21, "CY" => 28, "CZ" => 24, "DK" => 18, "DO" => 28, "TL" => 23, "EE" => 20, "FO" => 18, "FI" => 18, "FR" => 27,
+            "GE" => 22, "DE" => 22, "GI" => 23, "GR" => 27, "GL" => 18, "GT" => 28, "HU" => 28, "IS" => 26, "IE" => 22, "IL" => 23,
+            "IT" => 27, "JO" => 30, "KZ" => 20, "XK" => 20, "KW" => 30, "LV" => 21, "LB" => 28, "LI" => 21, "LT" => 20, "LU" => 20,
+            "MK" => 19, "MT" => 31, "MR" => 27, "MU" => 30, "MC" => 27, "MD" => 24, "ME" => 22, "NL" => 18, "NO" => 15, "PK" => 24,
+            "PS" => 29, "PL" => 28, "PT" => 25, "QA" => 29, "RO" => 24, "SM" => 27, "SA" => 24, "RS" => 22, "SK" => 24, "SI" => 19,
+            "ES" => 24, "SE" => 24, "CH" => 21, "TN" => 24, "TR" => 26, "AE" => 23, "GB" => 22, "VG" => 24
+        ];
+
+        $iban = mb_ereg_replace("/\s\-/", "", $iban); // sanitize for validation (remove spaces)
+        $country = mb_strtoupper(mb_substr($iban, 0, 2));
+
+        // we know the country the IBAN belongs to?
+        if(isset($country_length[$country])) {
+
+            // The IBAN matches in length and basic structure?
+            $matches = null;
+            if(mb_ereg_match('/^([A-Za-z]{2})(\d{2})([A-Za-z0-9]{' . $country_length[$country] . '})$/', $iban, $matches)) {
+                $checkNum = $matches[1];
+                $bban = strtoupper($matches[2]);
+
+                // Replace letters with digits (a or A => 11, b or B => 12,..)
+                $checkString = mb_ereg_replace_callback('/[A-Z]/', function ($matches) {
+                        return base_convert($matches[0], 36, 10);
+                }, $bban . $country . '00');
+
+                $int_iban = intval($checkString); // remove leading zeros by converting to int.
+
+                // calculate check number of IBAN and convert to string of length 2.
+                $calc_checkNum = 98 - bcmod($int_iban, 97);
+                $calc_checkNum = ($calc_checkNum < 10 ? "0$calc_checkNum" : "$calc_checkNum");
+
+                // Invalid if check number is not the same as the calculated one.
+                if ($calc_checkNum !== $checkNum) return false;
+            }
+            else
+                return false;
+
+        }
+
+        return true;
+    }
+
 }
\ No newline at end of file