Yes, as an admin you can invite multiple users to your Discourse groups by using the bulk invite feature.
This feature can be found directly on your User Profile → Invites page.
Instead of inputting emails one by one, you can upload a CSV file containing all the email addresses you wish to invite. The following comma separated information can be provided if you want to add people to groups or send them to a specific topic the first time they sign in.
name@example.com,first_group_name;second_group_name,topic_id
For more information about this process, we have a guide on Sending bulk user invites .