Here you go:

$language = \Drupal::languageManager()->getCurrentLanguage()->getId();
$user = \Drupal\user\Entity\User::create();

// Mandatory.
$user->setPassword('password');
$user->enforceIsNew();
$user->setEmail('email');
$user->setUsername('user_name');

// Optional.
$user->set('init', 'email');
$user->set('langcode', $language);
$user->set('preferred_langcode', $language);
$user->set('preferred_admin_langcode', $language);
$user->set('setting_name', 'setting_value');
$user->addRole('rid');
$user->activate();

// Save user account.
$result = $user->save();

Source

For Drupal 8, the code to create a user entity is the following one.

$language = \Drupal::languageManager()->getCurrentLanguage()->getId();
$user = \Drupal\user\Entity\User::create();

// Mandatory.
$user->setPassword('password');
$user->enforceIsNew();
$user->setEmail('email');
$user->setUsername('user_name');

// Optional.
$user->set('init', 'email');
$user->set('langcode', $language);
$user->set('preferred_langcode', $language);
$user->set('preferred_admin_langcode', $language);
$user->set('setting_name', 'setting_value');
$user->addRole('rid');
$user->activate();

// Save user account.
$result = $user->save();

The code can be found on Create a user account programmatically in Drupal 8.