Avast Software s.r.o. is a Czech multinational cybersecurity software company headquartered in Prague, Czech Republic. Avast has more than 435 million users and the largest market share among anti-malware application vendors worldwide as of January 2018.The company has approximately 1,700 employees across its 25 offices worldwide. It was founded by Pavel Baudiš and Eduard Kučera in 1988 as a cooperative. It had been a private company since 2010 and had its IPO in May 2018.

In July 2016, It acquired competitor AVG Technologies for $1.3 billion. At the time, AVG was the third-ranked antivirus product.

It is listed on the London Stock Exchange and is a constituent of the FTSE 250 Index.