Closest airport:

Denver International Airport (DEN)

Note: Nonstop Paris - Denver flights will begin in April 2018 on Norwegian Air

Ground Transportation Denver International Airport - Boulder

Airport shuttle service is available from Green Ride

Advance reservations are recommended. 

The one-way fare to and from Boulder hotels is $40 (not including tip).

Public Transportation: RTD

The Boulder-Denver International Airport route is AB (AB1/AB2)

The last stop on AB2 is Boulder Junction at Depot Square Station, which is next to the Hyatt Place Boulder.  If you can get it, that's great.  However, AB2 only runs on weekdays and only a couple of times in the am and evening.

AB1 will take you as far as the Boulder Downtown Station.  From there, you would need to book a taxi or take another bus.

You can find a Trip Planner on the RTD website.

You can find the AB schedule here

The one-way fare is $9.00.