Hundreds of male runners raced in three categories -- 21, eight and four kilometres -- in a contest that started and ended at the city's King Saud University and was called the "Riyadh Marathon".
Ethiopian runner Tamira Mola finished first, taking home the one million riyal cash prize.
Saudi sports authority chief Turki al-Sheikh tweeted pictures of the oldest Saudi to complete the race, 79-year-old Khalaf al-Balawi.
But some Saudis complained on social media of what they called wasteful spending as the kingdom reels from slumping oil revenues, high inflation and unemployment.
The kingdom's General Entertainment Authority on Thursday announced it will stage more than 5,000 festivals and concerts in 2018, double the number of last year, and pump $64 billion in the sector over the coming decade.
Riyadh hosted the kingdom's first-ever jazz festival on Friday, showcasing bands from Beirut and New Orleans.
Long known for its ultra-conservative mores, the kingdom has embarked on a wide-ranging programme of social reforms that includes allowing women to drive from June.
But at Saturday's marathon, some Saudis rued the absence of women.
"We need a marathon for women," one Twitter user said.