|This is not a Wikipedia article: It is an individual user's work-in-progress page, and may be incomplete and/or unreliable. For guidance on developing this draft, see Wikipedia:So you made a userspace draft.|
A Lego clone is a line or brand of children's construction blocks which is mechanically compatible with LEGO brand blocks, but is produced by another manufacturer. "Automatic Binding Bricks" were patented by the Lego Group in 1958, and the company has remained dominant in the plastic construction block market segment since. Several competitors in the segment have moved to take advantage of Lego's superior product recognition and large installed base by advertising their own products as compatible with Lego's.
At least two of the leading clone manufacturers have been challenged in court by Lego. The lawsuits have mostly been unsuccessful, as courts have generally found the functional design of the basic brick to be a matter of patent rather than trademark law, and all relevant Lego patents have expired.
The Canadian company Mega Bloks was sued on the grounds that its use of the "studs and tubes" interlocking brick system was a violation of trademarks held by Lego. On November 17, 2005, the Supreme Court of Canada upheld Mega Bloks' right to continue selling the product in Canada. A similar decision was reached by the European Union's Court of First Instance on November 12, 2008, upholding a EU regulatory agency's reversal of opinion following an objection by Mega Bloks against a trademark awarded to Lego in 1999. On September 14, 2010, the European Court of Justice ruled that the 8-peg design of the original Lego brick "merely performs a technical function [and] cannot be registered as a trademark." 
The English company Best-Lock Construction Toys was also sued by Lego in German courts in 2004  and 2009 . The German Federal Court denied Lego trademark protection for the shape of its bricks in the latter case.
The Lego Group did score a success in 2002, when its Swiss subsidiary Interlego AG sued the Tianjin COKO Toy Co., Ltd. company for copyright infringement. A claims court found many Coko bricks to be infringing; CoCo was ordered to cease manufacture of the infringing bricks, publish a formal apology in the Beijing Daily, and pay a small fee in damages to Interlego. On appeal, the Beijing High People's Court upheld the trial court's ruling..
Major clone manufactures
- Mega Bloks - based in Canada. The Lego Group's closest competitor, with a large product line, major third-party licences such as HALO, Smurfs, and Hello Kitty, and a presence in mainstream toy outlets.
- Best-Lock - based in England. Semi-compatible with Lego bricks, having the same length and width but a different height.
- Oxford - based in South Korea. Distributed in the West by Hasbro under the Kreo brand.
- Super Blox - a brand of the CRA-Z-ART company, based in the US.
- Rokenbok - based in the US. High-end educational sets.
- Tente - based in Spain, 1972-2008. Semi-compatible with Lego, having the same dimensions but a different stud diameter.
- EXÍN Castillos - based in Spain. Semi-compatible with Lego, having the same dimensions but a different stud diameter.
- Sluban - based in China.
- Cobi - based in Poland. Continues to be marketed independently since merging with Best-Lock in 2006.
- CoCo - produced by the Chinese company Tianjin COKO Toy Co., Ltd. until 2002.
- Built to Rule - a Transformers-based line from Hasbro.
- Ligao - based in China. A pirate brand; manufactures copies of Lego elements using pirated molds.
- Kazi - based in China. A pirate brand; manufactures copies of Lego elements using pirated molds.
- Enlighten - based in China. A pirate brand; manufactures copies of Lego elements using pirated molds.
- Wange - based in China. A pirate brand; manufactures copies of Lego elements using pirated molds.