Si Kak Phraya Si (Thai: สี่กั๊กพระยาศรี, pronounced [sìː kák pʰrā.jāː sǐː]) is an intersection in area of Wang Burapha Phirom sub-district, Phra Nakhon district, Bangkok. It is the intersection of Charoen Krung, Fueang Nakhon and Ban Mo roads. It is considered to be the second intersection of Charoen Krung, the first official street in Thailand, after nearby Saphan Mon (Mon bridge).

The term Si Kak Phraya Si can mean Phraya Si's intersection and comes from the Teochew word "角" (Kak) meaning angle or corner and "四" (Si) meaning four, refers to four-way intersection. Also, Phraya Si (พระยาศรี) was the name of Mon who had a house in this neighbourhood. He was an aristocrat and the recipient of a concession in the teak trade during the reign of King Mongkut (Rama IV). Phraya Si was the leader in the construction of Charoen Krung and Saphan Mon. In addition, there is also Soi Phraya Si (Phraya Si alley), another way named in his honour. It is an alley that connects Fueang Nakhon and Atsadang roads to the Saphan Hok (Lifting bridge), the pedestrian bridge over Khlong Lot (คลองหลอด; lit: tube canal). At this area, was the site of the first department store in Thailand – Harry A. Badman and Co., by Mr. Badman, British businessman in 1899 during the reign of King Chulalongkorn (Rama V).

So the name "Si Kak Phraya Si" is so named after the Chinese who were dragging the rickshaw through here during the reign of King Mongkut and still used as the official name until now. To this day, there're only two intersections with the prefixed "Si Kak" that are here and Si Kak Sao Chingcha (สี่กั๊กเสาชิงช้า) further north.

Besides, Si Kak Phraya Si was the site of the first café in Thailand named "Red Cross Tea Room" by Madam Cole (Edna S. Cole), an American woman who was founder of Kullasatri Wanglang School (present-day Wattana Wittaya Academy). The café opened in 1917 during the First World War to raise money for the Red Cross to help the Allies. The location was also home to many luxury restaurants for foreigners and the elite of Thai society, in the period before the revolution in 1932, alike another areas in Bangkok, such as Ratchawong in Chinatown, Silom, Surawong or Si Phraya in Bangrak.

The neighbourhood around the intersection was home to several historic properties.

The Bangkok Central Books Depot (กรุงเทพบรรณาคาร, Krungthep Bannakhan) was a bookshop and publisher, occupying a shophouse on Charoen Krung Road between the Si Kak Phraya Si and Saphan Than Intersection (now known as Chaloem Krung) to the east. The building was previously the practice of Takeda, a Japanese doctor. The bookshop opened there around 1932, after Phraya Niphonphotchanat (Santi Wichittranon), the head of the Royal Secretariat Department, left government service following the abolition of absolute monarchy. It was a leading bookshop at the time, mostly selling academic titles. Among other titles, it printed So Sethaputra's New Model English–Thai Dictionary and W.A.R. Wood's A History of Siam. The building was bombed during World War II, killing its owner, but his daughter later re-opened the shop in a nearby location; it is now known as Nibondh & Co., Ltd.