Fatikchhari (Bengali: ফটিকছড়ি, romanized: Fôṭikchhôṛi) is an upazila of Chittagong District in Chittagong Division, Bangladesh. It is the largest upazila of Chittagong.

The Fatikchhari Jami al-Uloom Fazil Madrasa and the Jamia Arabia Nasirul Islam Madrasa were founded in 1904 and 1912 respectively, transforming Fatikchhari into an important site of spiritual activities in the country. During the British colonial period, a thana was formed in Fatikchhari in 1918. In 1928, the Nanupur Sunnia Madrasa was established.

During the Bangladesh Liberation War, a training camp was founded in Fatikchhari by Mustafizur Rahman Siddiqi, Ziaur Rahman and Zonal Commander Mirza Abu Mansur in March 1971. Bengali freedom fighters around Chittagong that used to go to India for training purposes would return through there and Fatikchhari alone was home to roughly 1,500 Bengali freedom fighters. Thus Fatikchhari was regarded as the gateway to freedom fighters. Subsequently, the Abu Subhan School playground in Nanupur became a refugee camp. Mass graves were dug in Dantmara, Began Bazar, Darbar Sharif and Lelang Tea Garden.

It is one of the largest upazilas of Bangladesh. It is a fertile valley between the Sitakunda Hills and the Hills of the Chittagong Hill Tracts. These two hill ranges become one at the northernmost point of the upazila and they widen apart as they proceed southwards. There is no particular geographical place in the upazila called Fatikchhari, rather the entire upazila takes its name from one small all-season rivulet known as Fatikchhari Khal that originates in the Sitakundu Hills on the West and enters the Upazila at Bhujpur Union before joining the River Halda, the longest river in Fatikchhari Upazila that runs through the upazila along almost its entire length. Dhurung is its second longest river. There are some small rivers (khals) originating from the hills both on the eastern and western flanks, all being tributaries of the Halda flowing southwards to the sea. Among them are Gazaria, Fatikchhari, Baramasia, Mandakini, Balukhali etc. In between the two hill ranges, Fatikchhari consists of flat farmland annually affected by flash floods caused by heavy rainfall in the hilly catchment areas and the water being drained by several small rivers and the Halda.

It is surrounded by Tripura (India) to the north, Hathazari and Kawkhali Upazila (Rangamati District) to the south, Ramgarh, Manikchhari, Lakshmichhari, and Raozan Upazilas on the east, Mirsharai and Sitakunda Upazilas on the west.

According to the 2022 Bangladeshi census, Fatikchhari Upazila had 142,906 households and a population of 642,089. 10.71% of the population were under 5 years of age. Fatikchhari had a literacy rate (age 7 and over) of 76.11%: 78.16% for males and 74.24% for females, and a sex ratio of 93.18 males for every 100 females. 167,870 (26.14%) lived in urban areas. Ethnic population was 12,877 (2.01%), of which 8,991 were Tripura and 1313 Chakma.

As of the 2011 Census of Bangladesh, Fatikchhari upazila had 100,009 households and a population of 526,003. 126,792 (24.10%) were under 10 years of age. Fatikchhari had an average literacy rate of 51.35%, compared to the national average of 51.8%, and a sex ratio of 1025 females per 1000 males. 41,994 (7.98%) of the population lived in urban areas. Ethnic population was 11,919 (2.27%), of which Tripura were 6,857 and Chakma 1,038.

According to the 1991 Bangladesh census, Fatikchhari had a population of 388,013, in 65,861 households. Males constituted 50.1% of the population, and females 49.9%. The population aged 18 or over was 182,250. Fatikchhari had an average literacy rate of 32% (7+ years), against the national average of 32.4% literate.