How can I create a Magento 2 category programmatically
You need to load Magento 2 CategoryFactory model first and then create a new Magento 2 category.
$objectManager = \Magento\Framework\App\ObjectManager::getInstance();
$categoryFactory = $objectManager->get('Magento\Catalog\Model\Category');
$rootNodeId = 1; //root category id
$root = $categoryFactory->load($rootNodeId);
$category = "New Category";
$name=ucfirst($category );
$url=strtolower($category );
$cleanurl = trim(preg_replace('/ +/', '', preg_replace('/[^A-Za-z0-9 ]/', '', urldecode(html_entity_decode(strip_tags($url))))));
$categoryTmp = $categoryFactory->create();
$categoryTmp->setName($name);
$categoryTmp->setIsActive(true);
$categoryTmp->setUrlKey($cleanurl);
$categoryTmp->setData('description', 'description');
$categoryTmp->setParentId($rootNodeId);
$mediaAttribute = array ('image', 'small_image', 'thumbnail');
$categoryTmp->setImage('/new.png', $mediaAttribute, true, false);// Path pub/meida/catalog/category/new.png
$categoryTmp->setStoreId(1);
$categoryTmp->setPath($root->getPath());
$categoryTmp->save();