The company will also be removed from the ASX 200 All Australian index.
Galaxy shares are down by 57% so far this year due to falls in lithium prices due to oversupply.
West Africa-focused gold producer Perseus Mining will be added to the ASX 200 All Australian index.
The company's shares have risen by more than 150% this year due to the higher gold price and a strong operational performance at its Edikan gold mine in Ghana and newer Sissingue mine in Cote d'Ivoire.
Perseus is currently building a third mine, Yaoure, in Cote d'Ivoire, which is on schedule for first gold this time next year.
"With the inclusion into the S&P/ASX All Australian 200 index, the company gains further exposure across the global market and is now investable for certain large institutions whose mandates restrict them to investing in ASX 200-listed companies," Perseus said.
Newcrest Mining will join the ASX 20 index, while South32 will drop out.
S&P Dow Jones Indices said the changes would take effect on December 23.