His Soyuz spaceship landed at 16:31 local time (13:31 BST) this afternoon on the steppes of Kazakhstan after what Hungarian-born Mr Simonyi described as a journey which "wasn't as difficult as it could have been".
Accompanied by Russian cosmonauts, Fyodor Yurchikhin and Oleg Kotov, Mr Soyuz spent his spell on the International Space Station (ISS) conducting scientific experiments and eating food prepared by US celebrity domestic goddess Martha Stewart, with whom he is romantically linked.
"It's good to be back on Earth," Mr Simonyi, who before take-off had described himself as "the first nerd in space", said on landing.
Analysts say the enormous money spent by space tourists is vital funding for Russia's space programme.
Last year Anousheh Ansari became the first female space tourists to blast off, five years after Dennis Tito's historic $20 million (£10 million) week-long flight.
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