The 48-year-old retired footballer is accused of coercive and controlling behaviour towards Kate Greville in the second half of their six-year relationship.
She also claims he headbutted her during a final altercation at his £1.7 million mansion in Worsley, Greater Manchester, and Giggs is accused of assaulting Ms Greville’s sister Emma.
Giggs denied all the charges during a month-long trial at Manchester crown court.
After more than 22 hours of deliberations, the jury was today discharged after failing to reach verdicts on any of the charges.
The case has been adjourned until a hearing on September 7, when prosecutor Peter Wright QC is expected to announce whether the CPS will seek a retrial. He told the court a decision will be taken on whether it is in the public interest to pursue the case further.
The court heard a retrial – if sought – could take place in June next year.
Giggs, the former interim Manchester United manager and Wales national team boss, is accused of bombarding Ms Greville with messages, turning up unannounced at her home and gym, and reacting angrily when she accused him of cheating.
The star admits being unfaithful throughout his adult life, cheating on every woman he has been in a relationship with. But he insists he was neither controlling nor violent to Ms Greville.
It is said he headbutted her on November 1, 2020, when she tried to bring their relationship to an end.
Giggs denies any violence, and says any injury Ms Greville suffered was as a result of an accidental clash of heads. He also denies assaulting Emma Greville.
Giggs has been on bail since his arrest in November 2020, and will remain on bail while a decision is taken over the retrial.
He pleaded not guilty to coercive and controlling behaviour between 2017 and 2020, as well as allegations of assault occasioning actual bodily harm and common assault.
A juror had to be discharged from the case last week after falling ill, leaving the 11 remaining members to deliberate over possible verdicts.
However, a note was sent to Judge Hilary Manley this afternoon, indicating they were deadlocked. The jury foreman then confirmed in court that they had failed to reach verdicts on any of the charges.
Giggs – a 13-time Premier League winner with Manchester United, stood down from her role as Wales national manager to focus on the trial.