Carlo Allegri (1862–1938) was an Italian engineer who worked extensively in Siam (Thailand) during the turn of the 19th–20th centuries.

He served under the government of King Chulalongkorn (Rama V) for over 20 years, where he held the position of Engineer-in-Chief of the Public Works Department.

He oversaw the construction of numerous roads and bridges in the country and contributed to buildings such as the Ananta Samakhom Throne Hall.

In 1893, he became the chief engineer for the Ministry of Public Works and promptly hired 35 Italian staff members.

In 1907, he and his friends had designed Villa Norasingh that had a feeling of “Venice of the East” and they built a huge palace for King Rama V called the Ananta Samakhom Throne Hall.