Capsaicin is the chemical found in various hot peppers that causes the lips, the mucous membranes inside one's mouth, the esophagus and each end of the digestive tract to feel a burning sensation upon consumption, digestion and elimination, in addition to being the main ingredient in pepper spray. The hotness, or "acridity", of capsaicin is measured in Scoville Heat Units.

Please note: this list should be considered incomplete, as new super-hot pepper cultivars are appearing one at a time every few years, mostly thanks to a man named Ed Currie, one of the world's foremost pepper growers.

Additionally, the peppers listed below have a range of Scoville heat units rather than a static number. This is because there are a few factors that affect the pungency of peppers—weather conditions, mostly, but also soil quality and, as any grower would tell you, luck.

Many, if not most of those listed below following the ghost pepper, are cultivars and are not found in the wild.

Pepper name Scoville rating Country or region of origin
Bell0Mexico
Banana100—500South America
Pepperoncini (aka friggitelli)100—500Italy
Shishito100—1,000Japan
Padrón500—2,500Spain
Espelette500—4,000France
Española1,000—1,500New Mexico
Poblano1,000—2,000Mexico
Cascabel cherry1,000—2,500Mexico
Ancho de Pasilla1,000—4,000Mexico
Baklouti1,000—5,000Tunisia
Anaheim/Hatch (aka New Mexican)1,500—2,500USA
Jalapeño2,500—5,000Mexico
Black Hungarian2,500—15,000Hungary
Serrano5,000—15,000Mexico
Chile de Árbol15,000—30,000Mexico
Black Cobra20,000—40,000Venezuela
Cayenne30,000—50,000French Guiana
Pequin30,000—60,000Mexico
Dundicut30,000—100,000Pakistan
Chiltepín50,000—100,000Central/South America
Thai50,000—100,000Thailand
Peri-peri50,000—175,000Sub-Saharan Africa
Malagueta60,000—100,000Brazil
Siling Labuyo80,000—100,000Philippines
Datil100,000—300,000Florida
Scotch Bonnet100,000—350,000Brazil
Madame Jeanette100,000—350,000Suriname
Habanero200,000—500,000Mexico
Red Savina350,000—577,000California
Nagabon (Scotch Bonnet X Ghost Pepper)750,000—900,000UK
Naga Jolokia (aka Ghost Pepper)855,000—1,041,000India
7 Pot Douglah924,000—2,200,000Trinidad and Tobago
Naga Morich1,000,000—1,850,000Bangladesh
Naga Viper1,000,000—1,300,000UK
Infinity chili1,067,000—1,300,000UK
Trinidad Scorpion Butch T1,200,000—1,400,000Trinidad and Tobago
Komodo Dragon1,400,000—2,200,000UK
Genghis Khan's Brain1,500,000—1,700,000Italy
Carolina Reaper (Naga Viper X Habanero)1,569,000—1,700,000South Carolina
Trinidad Moruga Scorpion1,800,000—2,000,000Trinidad and Tobago
Dragon's Breath2,480,000—2,600,000UK
Pepper X3,180,000 +South Carolina

For reference, consumer-grade pepper spray rates about 2,000,000 and police-grade rates 4,500,000 Scoville units. Pure, unrefined capsaicin rates at 16,000,000 Scovilles.

It's a tricky proposition to eat any of the peppers (fresh and whole) listed above that come after the habanero; search Youtube for "eating carolina reaper" or "eating scorpion peppers" and it becomes abundantly clear that doing so causes most people severe gastrointestinal distress, making the consumption of such peppers more of a survival challenge than anything else. (Indeed, Dragon's Breath and Pepper X aren't even intended for human consumption; rather, those peppers are grown for use in anesthetic topical solutions, although at least one sauce has been made from Pepper X—Heatonist's "The Last Dab XXX", which has been featured on Hot Ones for a few years.) This isn't necessarily the case when those peppers are used to make hot sauces, but still, use caution and common sense when approaching heat level 10+.