Yes, but not at any of the major or minor hotel-casinos.
The lack of indoor-pool facilities can be attributed to two principal factors: cost and climate. With Vegas' scorching summers, almost every hotel has an outdoor pool, allowing guests a cool-down opportunity and, these days, often a social and entertainment scene to rival the city's famous nightlife offerings.
Also, virtually every major Strip hotel has at least one pool that's heated year-round, so you can still take a dip or get in your aqua workout, even if it's well outside of sunbathing season.
To maintain an indoor pool in addition to the outdoor water worlds isn't cost-effective, especially since it would probably see limited use, plus pools tend to take up a large amount of real estate.
For many years, the Tropicana was the only hotel on the Strip that operated a year-round indoor-outdoor heated pool, but that disappeared during a remodel (2011), so now the only hotel even near the Strip with an indoor pool is the non-gaming Platinum, located a few blocks east of the action on Flamingo Road. It's open year-round, but to hotel guests only unless you book a treatment in the spa, in which case you can also use the pool and the fitness center.
Smaller non-casino lodging places have small indoor-pool facilities. The Best Western Plus North and West Las Vegas properties each has an indoor heated pool, as does the Embassy Suites Convention Center -- all popular with business and convention travelers, as well as budget-conscious tourists.
If you're feeling adventurous, there are a couple of other options you can check out. On the west side of town, the Desert Breeze indoor pool and outdoor water park (located on Spring Mountain Rd. just east of Durango) has a nice indoor pool; adult admission is $3.
The east valley has the Hollywood Aquatic Center, where amenities include a 10-lane indoor competition pool, an indoor instructional pool, and an outdoor activity pool and water park.
Call (702) 455-8508 or visit the Clark County Parks and Recreation website for up-to-date information about schedules and activities at these and other pools in the valley.