CSL Limited is an Australian multinational specialty biotechnology company that researches, develops, manufactures, and markets products to treat and prevent serious human medical conditions.

CSL's product areas include blood plasma derivatives, vaccines, antivenom, and cell culture reagents used in various medical and genetic research and manufacturing applications.

[4] Under the first director, William Penfold,[5] CSL commenced operation in the vacant Walter and Eliza Hall Institute building at the Royal Melbourne Hospital in 1918 before moving to its purpose-built Parkville premises in the following year.

[6] Soon after Morgan's appointment, CSL was drawn into a serious public health disaster when a batch of its diphtheria toxin-antitoxin was implicated in the deaths of twelve children in what became known as the Bundaberg tragedy of 1928.

Although CSL's manufacturing processes were absolved, its labelling procedures were seen to be in error, leading to an enduring focus on the highest standards across the facility's production.

The relationship with the Hall Institute continued until World War II, particularly via joint projects on viral diseases including polio and influenza coordinated by Frank Macfarlane Burnet and Esmond "Bill" Keogh.

Seqirus has its headquarters in Maidenhead and has production facilities in Holly Springs, US, Liverpool, UK, and Parkville, Victoria CSL's vaccine for swine flu, the world's first, was approved in September 2009 for use by people over age 10.

On 28 September 2010, the Australian Therapeutic Goods Administration (TGA) conducted an analysis of febrile convulsions following immunisation in children following monovalent pandemic H1N1 vaccine (Panvax/Panvax Junior, CSL).

[28] A paper published in the Medical Journal of Australia provides a possible reason for CSL's 2010 flu vaccine causing febrile convulsions in children.

[32] On 23 March 2021, the Therapeutic Goods Administration provisionally approved the first batches, numbering 832,000 doses, of the Oxford–AstraZeneca COVID-19 vaccine manufactured by CSL in its plant in Broadmeadows, Victoria.