Saudi Arabia's allies and friends have congratulated the kingdom on its 91st National Day.
Sheikh Khalifa bin Zayed, UAE President, Sheikh Mohammed bin Rashid, Vice President and Ruler of Dubai, and Sheikh Mohamed bin Zayed, Crown Prince of Abu Dhabi and Deputy Supreme Commander of the Armed Forces, conveyed their best wishes.
Dr Anwar Gargash, presidential advisor and former minister of state for foreign affairs, tweeted his congratulations and reflected on the role Saudi Arabia plays in the region.
He "recalled the epic unification and inspiring historical leadership" of Saudi Arabia and said: "We are proud of the renaissance led by the Custodian of the Two Holy Mosques and his faithful Crown Prince, and we look forward to further development and prosperity for Saudi Arabia and its honourable people."
Thursday marks the day when the nation's founder, King Abdulaziz Al Saud, renamed the Kingdom of Nejd and Hejaz the Kingdom of Saudi Arabia, in honour of his family.
It was declared a national holiday by the late King Abdullah in 2005.
Bahrain's King Hamad and Prime Minister and Crown Prince Salman bin Hamad congratulated Saudi Arabia's King Salman and Crown Prince Mohammed bin Salman, praising the strong ties between the two nations.
In his message to the Saudi monarch, King Hamad "wished him abundant health, happiness and long life, as well as further progress and prosperity to the brotherly Saudi people," as well as the desire to deepen their "long-standing" relationship.
Bahrain also lit up several landmarks and buildings in green, the colour of Saudi Arabia's flag, to mark the occasion.
Bahrain's Speaker of the Council of Representatives, Fawzia bint Abdullah Zainal, also commended the kingdom's efforts in "safeguarding regional security and stability", the state-run Bahrain News Agency reported.
Ms Zainal said she is proud of the "pivotal role" Saudi Arabia plays "in preserving Arab and Islamic rights and freedoms".
Oman's Sultan Haitham bin Tarik and Qatar's Emir Sheikh Tamim bin Hamad Al Thani also sent their congratulations.
Sultan Haitham wished the king good health and for the Saudi people to "realise their aspirations of further progress and prosperity".
Meanwhile, Saudi National Day hashtags were trending on Twitter as people wished the country prosperity.
"Ninety-one years of glory, safety and development... How lucky we are to be among the sons of this country," one person wrote.
Another person tweeted a video of fireworks emerging from the Kingdom Centre tower in Riyadh with the caption: Happy National Day.
Fireworks are scheduled to take place across the country on Thursday, as well as a military parade and show featuring the Saudi Royal Airforce, known as the Saudi Hawks, along with government and private events.