Yes. Australian citizens need a visa to travel to Sri Lanka because Australia is not on the exemption list for Sri Lanka visas. Australian citizens now can apply for a Sri Lanka electronic visa which saves time and costs.
Since 2012, travelers who want to enter Sri Lanka for a short-term visit can take advantage of the Sri Lanka ETA. This type of online visa allows visitors to visit Sri Lanka for purposes such as tourism, business, or transit. The visa application process is simple and just takes the applicants a few minutes to complete.
Australian citizens who want to come to Sri lanka for other purposes such as study abroad, work, etc, need to apply for a visa at the Sri lanka consulate in Australia or anywhere.