diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index 499f552..bfee3a2 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -25,7 +25,7 @@
  * @todo Move this to an appropriate autoloadable class. See
  *   https://www.drupal.org/project/drupal/issues/2908079
  */
-const DRUPAL_MINIMUM_PHP = '5.5.9';
+const DRUPAL_MINIMUM_PHP = '7.0.0';
 
 /**
  * Minimum recommended version of PHP.
diff --git a/core/install.php b/core/install.php
index c88ffee..d367bce 100644
--- a/core/install.php
+++ b/core/install.php
@@ -25,8 +25,8 @@
 // The minimum version is specified explicitly, as DRUPAL_MINIMUM_PHP is not
 // yet available. It is defined in bootstrap.inc, but it is not possible to
 // load that file yet as it would cause a fatal error on older versions of PHP.
-if (version_compare(PHP_VERSION, '5.5.9') < 0) {
-  print 'Your PHP installation is too old. Drupal requires at least PHP 5.5.9. See the <a href="https://www.drupal.org/requirements">system requirements</a> page for more information.';
+if (version_compare(PHP_VERSION, '7.0.0') < 0) {
+  print 'Your PHP installation is too old. Drupal requires at least PHP 7.0.0. See the <a href="https://www.drupal.org/requirements">system requirements</a> page for more information.';
   exit;
 }
 
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index 960bb7d..b56fb8d 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -192,18 +192,10 @@ function system_requirements($phase) {
     // If PHP is old, it's not safe to continue with the requirements check.
     return $requirements;
   }
-  if ((version_compare($phpversion, DRUPAL_RECOMMENDED_PHP) < 0) && ($phase === 'install' || $phase === 'runtime')) {
-    // Warn if still on PHP 5. If at least PHP 7.0, relax from "warning" to
-    // "info", and show it at runtime only, to not scare users while installing.
-    if (version_compare($phpversion, '7.0') < 0) {
-      $requirements['php']['description'] = t('Drupal will drop support for this version on March 6, 2019. Upgrade to PHP version %recommended or higher to ensure your site can receive updates and remain secure. See <a href="http://php.net/supported-versions.php">PHP\'s version support documentation</a> and the <a href=":php_requirements">Drupal 8 PHP requirements handbook page</a> for more information.', ['%recommended' => DRUPAL_RECOMMENDED_PHP, ':php_requirements' => 'https://www.drupal.org/docs/8/system-requirements/php']);
-      $requirements['php']['severity'] = REQUIREMENT_WARNING;
-    }
-    else {
-      if ($phase === 'runtime') {
-        $requirements['php']['description'] = t('It is recommended to upgrade to PHP version %recommended or higher for the best ongoing support.  See <a href="http://php.net/supported-versions.php">PHP\'s version support documentation</a> and the <a href=":php_requirements">Drupal 8 PHP requirements handbook page</a> for more information.', ['%recommended' => DRUPAL_RECOMMENDED_PHP, ':php_requirements' => 'https://www.drupal.org/docs/8/system-requirements/php']);
-        $requirements['php']['severity'] = REQUIREMENT_INFO;
-      }
+  if (version_compare($phpversion, DRUPAL_RECOMMENDED_PHP) < 0) {
+    if ($phase === 'runtime') {
+      $requirements['php']['description'] = t('It is recommended to upgrade to PHP version %recommended or higher for the best ongoing support.  See <a href="http://php.net/supported-versions.php">PHP\'s version support documentation</a> and the <a href=":php_requirements">Drupal 8 PHP requirements handbook page</a> for more information.', ['%recommended' => DRUPAL_RECOMMENDED_PHP, ':php_requirements' => 'https://www.drupal.org/docs/8/system-requirements/php']);
+      $requirements['php']['severity'] = REQUIREMENT_INFO;
     }
   }
 
diff --git a/core/tests/Drupal/Tests/Core/Extension/ThemeExtensionListTest.php b/core/tests/Drupal/Tests/Core/Extension/ThemeExtensionListTest.php
index 9c5fd58..4514b70 100644
--- a/core/tests/Drupal/Tests/Core/Extension/ThemeExtensionListTest.php
+++ b/core/tests/Drupal/Tests/Core/Extension/ThemeExtensionListTest.php
@@ -260,5 +260,5 @@ class TestThemeEngineExtensionList extends ThemeEngineExtensionList {
 }
 
 if (!defined('DRUPAL_MINIMUM_PHP')) {
-  define('DRUPAL_MINIMUM_PHP', '5.5.9');
+  define('DRUPAL_MINIMUM_PHP', '7.0.0');
 }
diff --git a/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php b/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
index 97a5e93..b990f2c 100644
--- a/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
+++ b/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
@@ -147,5 +147,5 @@ protected function themeRegistryRebuild() {
 }
 
 if (!defined('DRUPAL_MINIMUM_PHP')) {
-  define('DRUPAL_MINIMUM_PHP', '5.5.9');
+  define('DRUPAL_MINIMUM_PHP', '7.0.0');
 }