White rings on a wood table are usually moisture trapped in or under the finish—not a stain deep in the wood. Cups and humid air are the usual causes.
White vs dark marks
White or cloudy marks sit in the finish and often respond to gentle heat or a finish refresh. Dark rings mean water reached the wood; those need sanding and refinishing of the affected area.
Low-risk methods first
Place a dry cotton cloth over the ring and iron on low with no steam in short passes. Check often. A small dab of non-gel toothpaste or baking soda paste rubbed lightly can reduce mild haze—wipe clean and polish afterward. Stop if color changes.
When ironing is not enough
If the mark remains, level and recoat the finish. For dark water stains in the wood, sand to clean fiber, treat tannin stains only if needed, restain, and finish.
Protect afterward
Coasters and trivets prevent repeats. Wipe spills promptly on oil finishes, which are more open than film finishes.
For more repairs like this, start in the Furniture Repair hub. If you are working through a related problem next, see Wood Veneer Repair: Professional Tips for a Seamless Finish or Wood Veneer Burnthrough Repair: Fixing Sanding Mistakes.
