Organ theft

Organ theft is the forcible removal of a person's organs to be used as transplants and sold on the black market. While some supposed cases of organ theft are urban legends, others have been found to be true. It is also a commonly used trope in science fiction.
The urban legend.
As an urban legend the story has been around since at least the early 1990s and mostly involves the theft of one or both of the victims kidneys. According to Jan Harold Brunvand it's possible that the story originated due to a news story wherein a Turkish man, Ahmet Koc, claimed to have had his kidney stolen at a hospital but had in fact sold his kidney and was unhappy at the amount of money he'd been paid.
There is certainly a worldwide organ trafficking issue but actual organ theft is highly unlikely. Benjamin Radford notes that organ transplantation is extremely complicated, requires specific matches coupled with fairly tight time frames, and highly specialized medical training. As such, the common variations on the legend where either a lone traveler is drugged or otherwise subdued or where a child is kidnapped and harvested against their will are simply not possible scenarios for such theft to occur.
Credible occurrences.
There are some cases that have been proven or are at least strongly suspected to be real occurrences. As you can read below these are generally institutional settings with the systems and expertise available for the transplantation of the organ to occur.
China.
According to reports there are more organ donations than there are official donors and it's suspected that prisoners of conscience are making up the difference against their will. The U.S. House of Representatives and the European Parliament have passed resolutions condemning the practice.
The allegations are strongly supported by a 2017 report. The report itself is an update to two separate works of investigative journalism:
On June 17, 2019 the China Tribunal, an independent tribunal looking into the accusations of forced organ harvesting in China, released their final report and judgement. The tribunal in part determined that:
As a result of the tribunal's report and China previously admitting to harvesting organs (although they claimed to have ceased the practice in 2015) several prominent journals are instituting stronger controls to ensure that papers produced on organ transplantation only use voluntarily obtained organs.
India.
The multi-billion rupee Gurgaon kidney scandal came to light in January 2008 when police arrested several people for running a kidney transplant racket in Gurgaon, an industrial township near New Delhi, India. Kidneys from most of the victims, who were the poor hailing from the nearby western Uttar Pradesh, were transplanted into clients from the United States, United Kingdom, Canada, Saudi Arabia and Greece. The police raid was prompted by complaints by the locals from Moradabad about illegal kidney sales. The man accused of the scandal, Amit Kumar, was arrested in Nepal on 7 February 2008 and has denied any hand in criminal activity. According to the Gurgaon police, the scandal at a local clinic was going on for six to seven years. The donors were lured with offerings of about Rs. 30,000 for kidney removal. First, they were lured to the clinic on the pretext of job opportunities. They were instead asked for donating their kidneys for the fee and all those who resisted this were drugged against their will and subsequently operated upon.
Kosovo.
Organ theft in Kosovo has been widely reported.
In science fiction.
Organ theft is a common trope in science fiction, being popularized by the Known Space universe created by Larry Niven, where it is called "organlegging", a portmanteau of "organ" and "bootlegging". Due to organ transplantation becoming safe and universally effective, a huge potential black market in body parts was able to be exploited by murderous racketeers.