"Henry Danger" star Cooper Barnes is being dragged into a legal spat between his actress wife and their female neighbor ... his wife says their neighbor is trying to seduce him and sabotage their marriage.

According to new legal docs, obtained by TMZ, Cooper's wife Liz Stewart is suing a woman named Jessica Ray ... claiming Jessica's a single mom who moved into their condo complex and developed the hots for Cooper.

In the suit, Liz claims Jessica has been trying to seduce Cooper for a while now ... sending him texts and trying to get him over to her place ... alone.

Among the alleged texts Liz claims Jessica sent Cooper ... "have your wife put your daughter to bed while you come to the jacuzzi with me, so we can talk alone."

Liz also claims Jessica texted Cooper to "come over and help me open this bottle of wine" ... and she says Jessica tried to get a photo of him by texting "I love toilet selfies."

In the docs, Liz claims Jessica goes out of her way to play cornhole in front of their home and showed up to the community pool in nothing but a skimpy bikini for a birthday party for Liz and Cooper's 8-year-old daughter ... claiming Jessica left her own kid at home.

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Liz claims Jessica is not being discreet in the condo complex and she says the alleged seduction could ruin Cooper's career as a children's TV show star.

Cooper's wife is suing for intentional infliction of emotional distress and is going after Ray for damages.