One of the "Ying Yang Twins" -- Deongelo Holmes -- is already a free man ... after serving just 24 hours behind bars for beating his wife.
According to Georgia court docs -- obtained by TMZ -- Holmes made a deal and pled no contest to domestic violence for hitting Porsche in the head last November.
Under the deal, Holmes served a single day in jail and he's on probation for a year.
Holmes also has to do community service and attend a family violence program ... and he's been warned not to drink or do drugs ... or engage in any violent contact with his wife.