diff --git a/README.md b/README.md
index 3f28be08..ae05d50e 100644
--- a/README.md
+++ b/README.md
@@ -164,6 +164,10 @@ class MyCustomLink extends Link
 }
 ```
 
+## Custom link validation
+
+Custom links can have validation set using standard [model validation]([https://docs.silverstripe.org/en/5/developer_guides/forms/validation/#model-validation).
+
 ## Migrating from Shae Dawson's Linkable module
 
 https://github.com/sheadawson/silverstripe-linkable
diff --git a/lang/en.yml b/lang/en.yml
index 37f9f86e..59d7e554 100644
--- a/lang/en.yml
+++ b/lang/en.yml
@@ -16,14 +16,15 @@ en:
     SINGULARNAME: 'Email Link'
     db_Email: Email
   SilverStripe\LinkField\Models\ExternalLink:
-    EXTERNAL_URL_FIELD: 'External url'
+    EXTERNAL_URL_FIELD: 'External URL'
+    EXTERNAL_URL_FIELD_DESCRIPTION: 'The URL must include a protocol such as http:// or https://'
     LINKLABEL: 'Link to external URL'
     PLURALNAME: 'External Links'
     PLURALS:
       one: 'An External Link'
       other: '{count} External Links'
     SINGULARNAME: 'External Link'
-    db_ExternalUrl: 'External url'
+    db_ExternalUrl: 'External URL'
   SilverStripe\LinkField\Models\FileLink:
     CANNOT_VIEW_FILE: 'Cannot view file'
     FILE_DOES_NOT_EXIST: 'File does not exist'
diff --git a/src/Models/EmailLink.php b/src/Models/EmailLink.php
index 2b074161..dde0ea0e 100644
--- a/src/Models/EmailLink.php
+++ b/src/Models/EmailLink.php
@@ -4,6 +4,8 @@
 
 use SilverStripe\Forms\EmailField;
 use SilverStripe\Forms\FieldList;
+use SilverStripe\Forms\CompositeValidator;
+use SilverStripe\Forms\RequiredFields;
 
 /**
  * A link to an Email address.
@@ -55,4 +57,11 @@ public function getMenuTitle(): string
     {
         return _t(__CLASS__ . '.LINKLABEL', 'Link to email address');
     }
+
+    public function getCMSCompositeValidator(): CompositeValidator
+    {
+        $validator = parent::getCMSCompositeValidator();
+        $validator->addValidator(RequiredFields::create(['Email']));
+        return $validator;
+    }
 }
diff --git a/src/Models/ExternalLink.php b/src/Models/ExternalLink.php
index c724d906..a0bae240 100644
--- a/src/Models/ExternalLink.php
+++ b/src/Models/ExternalLink.php
@@ -3,6 +3,9 @@
 namespace SilverStripe\LinkField\Models;
 
 use SilverStripe\Forms\FieldList;
+use SilverStripe\Forms\CompositeValidator;
+use SilverStripe\Forms\RequiredFields;
+use SilverStripe\Forms\UrlField;
 
 /**
  * A link to an external URL.
@@ -27,8 +30,13 @@ class ExternalLink extends Link
     public function getCMSFields(): FieldList
     {
         $this->beforeUpdateCMSFields(function (FieldList $fields) {
-            $linkField = $fields->dataFieldByName('ExternalUrl');
-            $linkField->setTitle(_t(__CLASS__ . '.EXTERNAL_URL_FIELD', 'External url'));
+            $field = UrlField::create('ExternalUrl');
+            $field->setTitle(_t(__CLASS__ . '.EXTERNAL_URL_FIELD', 'External URL'));
+            $field->setDescription(_t(
+                __CLASS__ . '.EXTERNAL_URL_FIELD_DESCRIPTION',
+                'The URL must include a protocol such as http:// or https://'
+            ));
+            $fields->replaceField('ExternalUrl', $field);
         });
         return parent::getCMSFields();
     }
@@ -51,4 +59,11 @@ public function getMenuTitle(): string
     {
         return _t(__CLASS__ . '.LINKLABEL', 'Link to external URL');
     }
+
+    public function getCMSCompositeValidator(): CompositeValidator
+    {
+        $validator = parent::getCMSCompositeValidator();
+        $validator->addValidator(RequiredFields::create(['ExternalUrl']));
+        return $validator;
+    }
 }
diff --git a/src/Models/FileLink.php b/src/Models/FileLink.php
index 452d7684..c0c8afbb 100644
--- a/src/Models/FileLink.php
+++ b/src/Models/FileLink.php
@@ -4,6 +4,8 @@
 
 use SilverStripe\Assets\File;
 use SilverStripe\Forms\FieldList;
+use SilverStripe\Forms\CompositeValidator;
+use SilverStripe\Forms\RequiredFields;
 
 /**
  * A link to a File in the CMS
@@ -71,4 +73,11 @@ public function getMenuTitle(): string
     {
         return _t(__CLASS__ . '.LINKLABEL', 'Link to a file');
     }
+
+    public function getCMSCompositeValidator(): CompositeValidator
+    {
+        $validator = parent::getCMSCompositeValidator();
+        $validator->addValidator(RequiredFields::create(['File']));
+        return $validator;
+    }
 }
diff --git a/src/Models/PhoneLink.php b/src/Models/PhoneLink.php
index 0a72031b..a509c4ab 100644
--- a/src/Models/PhoneLink.php
+++ b/src/Models/PhoneLink.php
@@ -3,6 +3,9 @@
 namespace SilverStripe\LinkField\Models;
 
 use SilverStripe\Forms\FieldList;
+use SilverStripe\Forms\CompositeValidator;
+use SilverStripe\Forms\RequiredFields;
+use SilverStripe\LinkField\Form\PhoneField;
 
 /**
  * A link to a phone number
@@ -25,8 +28,8 @@ class PhoneLink extends Link
     public function getCMSFields(): FieldList
     {
         $this->beforeUpdateCMSFields(function (FieldList $fields) {
-            $linkField = $fields->dataFieldByName('Phone');
-            $linkField->setTitle(_t(__CLASS__ . '.PHONE_FIELD', 'Phone'));
+            $field = $fields->dataFieldByName('Phone');
+            $field->setTitle(_t(__CLASS__ . '.PHONE_FIELD', 'Phone'));
             $fields->removeByName('OpenInNew');
         });
         return parent::getCMSFields();
@@ -50,4 +53,11 @@ public function getMenuTitle(): string
     {
         return _t(__CLASS__ . '.LINKLABEL', 'Phone number');
     }
+
+    public function getCMSCompositeValidator(): CompositeValidator
+    {
+        $validator = parent::getCMSCompositeValidator();
+        $validator->addValidator(RequiredFields::create(['Phone']));
+        return $validator;
+    }
 }
diff --git a/src/Models/SiteTreeLink.php b/src/Models/SiteTreeLink.php
index 023ec7c9..aed10875 100644
--- a/src/Models/SiteTreeLink.php
+++ b/src/Models/SiteTreeLink.php
@@ -8,6 +8,8 @@
 use SilverStripe\Forms\FieldList;
 use SilverStripe\Forms\TextField;
 use SilverStripe\Forms\TreeDropdownField;
+use SilverStripe\Forms\CompositeValidator;
+use SilverStripe\Forms\RequiredFields;
 
 /**
  * A link to a Page in the CMS
@@ -147,4 +149,11 @@ public function getMenuTitle(): string
     {
         return _t(__CLASS__ . '.LINKLABEL', 'Page on this site');
     }
+
+    public function getCMSCompositeValidator(): CompositeValidator
+    {
+        $validator = parent::getCMSCompositeValidator();
+        $validator->addValidator(RequiredFields::create(['PageID']));
+        return $validator;
+    }
 }