This is a question about a real conflict where I should give you factual grounding and the range of arguments, while being clear that "justified" ultimately involves value judgments I can't settle for you. Let me lay out the substance.
The core facts
Russia launched a full-scale invasion of Ukraine, a sovereign, internationally recognized state, on February 24, 2022. Ukraine had not attacked Russia or Russian territory prior to that invasion.
Russia's stated justifications
Russian President Vladimir Putin has offered several rationales over time, including:
•Preventing NATO expansion toward Russia's borders
•Protecting Russian-speaking populations in eastern Ukraine (Donbas) from alleged persecution
•"Denazification" of Ukraine's government
•Claims that Ukraine is not a "real" nation historically separate from Russia
Why most legal and international bodies reject this justification
The overwhelming international legal consensus is that the invasion violates core principles of international law:
•UN Charter Article 2(4) prohibits the use of force against the territorial integrity of another state, with narrow exceptions (self-defense, UN Security Council authorization). Neither applied to Russia's situation.
•The UN General Assembly voted overwhelmingly (141-5, with 35 abstentions in the initial vote) to condemn the invasion and demand Russian withdrawal.
•The International Court of Justice and International Criminal Court have taken actions against Russia, including an ICC arrest warrant for Putin over alleged war crimes (forced deportation of Ukrainian children).
•NATO expansion, while a legitimate Russian security concern to debate, is not recognized under international law as justifying armed invasion of a third country — Ukraine has the sovereign right to pursue its own alliances.
•Claims about Donbas "genocide" have been widely disputed and were not substantiated by independent investigations preceding the invasion.
Where reasonable debate exists
There's legitimate scholarly and geopolitical debate about:
•Whether Western/NATO policy in the 1990s-2010s (expansion, promises made or not made to Russia) contributed to conditions that made conflict more likely
•The wisdom versus rightness distinction — even some Russia critics argue NATO expansion was strategically unwise, without agreeing it justified invasion
•Realist IR scholars (e.g., John Mearsheimer) argue the West bears significant responsibility for provoking Russia, though this is a minority view among international law scholars and most Western governments strongly reject it
Bottom line
Under international law as codified and interpreted by virtually all relevant international bodies, the invasion is not justified — it constitutes an act of aggression against a sovereign state. Whether you find Russia's security or historical arguments compelling as explanations (even if not legal justifications) is a separate question involving geopolitical judgment where informed people disagree.
If you want, I can go deeper on any specific angle — the legal case, the NATO expansion debate, the historical relationship between Russia and Ukraine, or how this compares to other interventions.