The ornamental orchid trade is global and comprises both a large, well-established legal market and a significant but largely unknown illegal trade. Much, though not all, of this illegal trade is driven by demand from specialist collectors for rare species. The trade in wild-harvested plants can have a severe impact on biodiversity: in one documented case, intense demand for a rare species of slipper orchid saw it harvested to near extinction. Illicit sales of wild orchids have been recorded on several online platforms, including e-commerce and social-media websites, forums and private websites, and sellers encompass both hobbyists and formal businesses. Consumers range from houseplant buyers, who want to purchase attractive plants, to specialist growers with a preference for rare species. For consumers who want to avoid illegal avenues of trade, and for researchers and law enforcement who want to monitor the trade, legality can be difficult to determine. However, it can be possible if the plant’s origin, species and final destination can be identified. This brief makes a substantial contribution to our ability to identify illicit orchid trade and the platforms most likely to host it.