Not just yet; the event must either sell tickets or collect RSVPs. A popular workaround is to set up free “RSVP Tickets” which can accompany your paid tickets. You can customize these tickets to collect guest information or allow free admittance.
When creating a new ticket, set the price at $0.00 and select the "Make this an RSVP Ticket" option as shown below:
Note: Of course, free for your guests means free for you too! There are no ticketing fees for $0.00 tickets.