The wife of President Barack Obama was part of a stream of American dignitaries in the ultraconservative desert kingdom on Tuesday.
Mrs Obama did not cover her head during the Riyadh visit, which is often standard for Western women visiting the kingdom but forbidden for Saudi women.
Saudi Arabia imposes a strict interpretation of Islamic law, forbidding women to work or travel without the authorisation of their male guardians.
It is also the only country in the world that bans women from driving, and a woman cannot obtain an identification card without the consent of her guardian. Floggings and death sentences are also commonplace.
Mrs Obama was pictured grimacing several times during the four-hour visit, which saw some members of the all-male Saudi delegation shake her hand, while others simply nodded at her as they passed by.
Earlier that day, her husband had spoken at length about the importance of women's rights during an address in India, setting up a jarring contrast with his warm embrace of Saudi Arabia.
On Twitter, some used hashtags to criticize Mrs Obama for being disrespectful of Saudi traditions, translating as #Michelle_Obama_Immodest and #Michelle_Obama_NotVeiled, Politico reports.
I actually do not appreciate her disrespect. Regardless of personal feelings and beliefs, 1 #Michelle_Obama_NotVeiled— Mony Al-Ali (@MonaBadah) January 28, 2015
she was a guest in another country &culture.She should make no judgements, but show proper respect at a funeral.2 #Michelle_Obama_NotVeiled— Mony Al-Ali (@MonaBadah) January 28, 2015
However it was also noted that Mrs Obama did chose to cover her hair during a visit to Istiqlal mosque in Indonesia in 2010. It is not a requirement for non-Muslim women to wear head-coverings at the holy site, but a sign of the Obama's efforts to show respect for the Islamic world, Reuters reported.
Al Ahram wrote: "However, some Saudis on social media also said that they understood that it was a short visit and urged others not criticise the wife of the kingdom's most important ally. One woman even asked her fellow Saudis on Twitter not to 'make Obama angry at us'."
It had been reported that a Saudi television station had blurred Mrs Obama’s face in footage of the meeting, but that has been denied by Saudi officials, Bloomberg View reports.
Some social media users posted screenshots apparently showing the First Lady obscured, though others reported seeing the same meeting without the pixellation.
Obama, like his recent predecessors, defended his willingness to forge close ties with the kingdom despite its array of human rights issues.
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"Sometimes we need to balance our need to speak to them about human rights issues with immediate concerns we have in terms of counterterrorism or dealing with regional stability," Obama said in an interview with CNN.
Two Saudis were beheaded for incest and smuggling amphetamine pills, while a Pakistani was executed for trafficking heroin into the kingdom.
Obama's presence underscored the key role Saudi Arabia plays in U.S. foreign policy in the Middle East and highlighted Washington's willingness to put national security priorities ahead of concerns about human rights issues.
Earlier on Tuesday, Obama had told an audience of young people in New Delhi that every woman should "be safe and be treated with the respect and dignity that she deserves."
A senior administration official said Obama raised the issue of human rights broadly in his discussions with the new King Salman, but did not tackle specific matters, including the case of a Saudi blogger who was convicted of insulting Islam and sentenced to 10 years in prison and 1,000 lashes.
The president cut short his trip to India to visit Saudi Arabia after 90-year-old Abdullah's death on Friday.
Obama was joined in Riyadh by Secretary of State John Kerry, along with Condoleezza Rice and James Baker, who led the State Department under Republican presidents. Former White House national security advisers Brent Scowcroft, Sandy Berger and Stephen Hadley also made the trip, as did Sen. John McCain, the Arizona Republican who is a frequent critic of Obama's foreign policy in the Middle East.
CIA Director John Brennan and Gen. Lloyd Austin, commander of U.S. Central Command, which overseas military activity in the Middle East, joined the delegation.