Tammy Swanson is the first ex-wife of Ron Swanson.
Tammy is cold and manipulative. She can force Ron to do anything she wants, turning him into a "neutered wimp" as Leslie Knope puts it. She can scare and manipulate anyone she comes across (her abilities have yet to be tested on someone super positive like Chris Traeger) as Ron's second ex-wife, Tammy 2, was seen fleeing from her.
Tammy is an IRS Agent and, as Ron put it, taught him everything he knows. She was not only a candy striper who helped deliver him, but she also taught him middle school math, Sunday school, driver's ed, and the art of sex. Their relationship was started when Ron was fifteen.
At some point in time, they got married. It is mentioned in the episode "Summer Catalog" that she threw a surprise birthday party for him. Ron saw some faces in his window and drove down to a gas station. He called the police and ever since has not liked surprises.
In "Li'l Sebastian," Donna Meagle rushes up to Ron, telling him his ex-wife is back. Since he's standing next to Tammy 2, he's confused at first. However, Donna informs him it's the other ex-wife and she's waiting in his office. Hearing this causes Tammy II to exclaim "oh shit" and rush off.
Tammy shows up at the end of "I'm Leslie Knope," claiming Ron is being audited. He says he doesn't care, but his mustache is trembling as he says it. In "Ron and Tammys," Ron is reluctant to listen to Tammy but eventually realizes he has to do what she says or he will go to jail. She forces Ron to share his bank accounts, house and financial information with her so that she can help, even convincing him making his bank accounts into joint accounts would be helpful. She scares Andy Dwyer and Leslie into not intervening.
April Ludgate is impressed by her, saying she is the "cold, distant mother I never had" and also takes her advice to "sit up straight; you're not doing your breasts any favors." It turns out, however, that Ron was not being audited at all and that Tammy 1 simply wanted to know where the gold that Ron owns is buried, as well as to know how much money he had in his accounts to know if she wanted to have a future with him. She claims she has found it but Ron reveals that it was fools' gold.
Ron's mother Tamara shows up and challenges her to a "prairie drink-off" of highly alcoholic Swanson family mash liquor, saying Ron will return to the farm forever if she wins. Leslie enters the drinking contest to save Ron from his mother and ex-wife, but the liquor immediately makes her too drunk to continue. Ron, finally fed up over people controlling him, chugs the jug dry and tells both Tammys to leave him alone.