Thanks everyone who replied. I was just reading "The World After Gaza" by Pankaj Mishra, and this was one of the statements made -- actually, I think more like "one of the most important". It really struck me what a Global North mindset I have, and not realizing how important this process has been. Anyway, I'd say "No, but..." (I think development of computers was probably more important) But I think it's very high up there.

@evan many of them wouldn't be alive to appreciate it at all were it not for maternal health initiatives.
https://pmc.ncbi.nlm.nih.gov/articles/PMC9292773/
See also vaccination (which started in the 1800's to be fair):
https://pmc.ncbi.nlm.nih.gov/articles/PMC4078488/
But most importantly, decolonization of India is not "achieved" yet, as others pointed out: https://blogs.lse.ac.uk/humanrights/2023/07/12/beyond-the-raj-how-british-colonialism-continues-to-impact-human-rights-in-india/
@evan
"Yes, but", it bleeds into so many other huge events, and it's so diffuse, geographically and chronologically, that it's pushing the definition of "event" to the limit.
"Global technological progress" is probably bigger than "decolonisation", but that's definitely a category not an event, even though it spans a similar timescale and geographical spread.