The Old Siam Plaza (Thai: ดิโอลด์สยามพลาซ่า) is a shopping mall in Wang Burapha, a historic neighbourhood of Bangkok, Thailand.

It is surrounded by Tri Phet, Burapha, Phahurat and Charoen Krung roads, and is near other neighbourhoods such as Yaowarat, Pak Khlong Talat or Ban Mo.

The mall is on the site of the former Ming Mueang market, part of notable Wang Burapha commercial and entertainment district.

In this way, many buyers who purchased fabrics in Phahurat later went in search of the seamstresses of Ming Mueang to make dresses for them.

[2] After operating for 30 years, in 2023 The Old Siam Plaza undertook a major renovation costing 400 million baht to become the first mixed-use lifestyle on Rattanakosin Island.