Yes, Southwest Airlines offers up to two checked bags per passenger for free on all of their flights. This applies to both domestic and international flights, and the bags can weigh up to 50 pounds each and have maximum dimensions of 62 inches (length + width + height).
In addition to the free checked bags, passengers are also allowed one carry-on bag and one personal item (such as a purse, briefcase, or laptop bag) for free. The carry-on bag can have maximum dimensions of 10 x 16 x 24 inches and must fit in the overhead bin, while the personal item must fit under the seat in front of you.