How to check admin user is login in Magento 2?

You can check the Admin user is login or not using Magento 2 with Backend Session class.

Full path:
Magento\Backend\Model\Auth\Session

You need to create an injectable class in the __construct() method to check the admin user is login.

<?php
namespace Jesadiya\AdminUser\Model;

use Magento\Backend\Model\Auth\Session;

class IsLogin
{
    /**
     * @var Session
     */
    private $backendSession;

    public function __construct(
        Session $backendSession
    ) {
        $this->backendSession = $backendSession;
    }

    /**
     * is login admin user
     *
     * @return bool 
     */
    public function isAdminLogin(): bool
    {
        return $this->backendSession->getUser() && $this->backendSession->getUser()->getId();
    }
}

The output will be boolean based on the user login status.