The 45-year-old was formally acquitted just days before his trial was due to start at the Old Bailey after “new material” emerged undermining the prosecution case.
Begg, who suffers from post-traumatic stress, has already spent seven months in custody in the high-security Belmarsh.
Appearing in court via video link from prison, he showed no reaction as Mr Justice Wilkie directed that he be formally found not guilty during a five-minute hearing at the Old Bailey.
Prosecutor Christopher Hehir told the court: “When Mr Begg was charged with a number of offences earlier this year, the Crown Prosecution Service were satisfied there was sufficient evidence to afford prosecution.”
Begg had been due to go on trial on Monday charged with seven counts. The first related to attending a terrorism training camp in Syria between October 9, 2012 and April 9, 2013.
The next five charges were for the possession of “an article” for a purpose connected to terrorism between December 31, 2012 and February 26, 2014.
They were listed as being electronic documents with the titles Camp 1, Camp 2, Tactical Training Schedule, Camp Rules, and Fitness Training Schedule (training exercises).
Finally, Begg, of Boden Road, Hall Green, Birmingham, was charged with funding terrorism by making available a Honda generator between July 14 and July 26, 2013. He denied all the charges against him. Begg spent two years in the notorious detention camp Guantanamo Bay.
Originally from Sparkhill, Birmingham, Mr Begg was held by the US in Camp X-Ray at the controversial Cuban jail from February 2003 until he was released without charge in January 2005.
The then 33-year-old was arrested in Islamabad, Pakistan in 2002 on suspicion of links with the Taliban or al Qaeda.