The Mass Effect timeline begins with a discovery and ends with a choice that determines the fate of all life in the galaxy. The discovery happens on 30 July 2148, when archaeologists excavating ruins on Mars find evidence of a civilisation far older and more advanced than humanity: the Protheans, who vanished approximately 50,000 years before the events of the games. The technology they left behind, centred on element zero and the manipulation of mass effect fields, accelerates human development by centuries and opens the door to faster-than-light travel through a network of ancient relay stations scattered across the galaxy.
Humanity's entry into galactic civilisation is not smooth. The First Contact War of 2157 establishes the pattern that will define human relations with the galaxy's other species for the next three decades: assertive expansion, military capability that surprises expectations, and a political determination to be taken seriously by a Citadel Council that has managed interstellar affairs for millennia without human involvement. By 2165, humanity has a seat at the table, if not yet an equal one.
The main trilogy covers the period from 2183 to 2186, during which Commander Shepard rises from decorated soldier to the central figure in a conflict that determines whether the galaxy survives. The threat is the Reapers, a civilisation of synthetic-organic entities that have been harvesting advanced species on a cycle lasting roughly 50,000 years, the same interval that separates the Prothean extinction from the present day. The trilogy's three endings represent three different resolutions to that conflict, each with irreversible consequences for every species in the Milky Way. Mass Effect: Andromeda then jumps 600 years forward and an entire galaxy away, to 2820, where a separate group of colonists is navigating a new beginning entirely disconnected from whatever ending the original trilogy produced.
The Prothean civilisation, which dominated the galaxy for 50,000 years, was harvested by the Reapers during the previous extinction cycle. Their ruins, scattered across multiple worlds, are the primary source of technological advancement for every species that comes after them, including humanity.
Open record →Archaeologists excavating ruins on Mars uncover evidence of the Protheans and the principles of mass effect physics. The discovery compresses centuries of technological development into decades and positions humanity for rapid interstellar expansion.
Open record →Humanity activates a dormant mass relay, opening instantaneous travel across interstellar distances. The activation brings humanity into contact with the wider galaxy and, eventually, with the species that have been using the relay network for millennia.
Open record →Earth's nations unify their interstellar interests under the Systems Alliance, a governmental and military body responsible for managing human expansion and relations with other species. It becomes the primary political entity representing humanity throughout the trilogy.
Open record →Turian patrol forces open fire on a human vessel activating a mass relay without Citadel authorisation. The conflict that follows is brief but significant, establishing both humanity's military credibility and the political complications that come with being a new species in a galaxy with established rules.
Open record →The Citadel Council brokers an armistice between humanity and the turians. The war lasts approximately two months. Its conclusion brings humanity formally into Citadel space under terms that acknowledge military capability without yet granting political equality.
Open record →The Systems Alliance is granted associate membership of the Citadel Council, giving humanity a formal voice in galactic governance for the first time. Full Council membership remains a point of contention throughout the trilogy.
Open record →Commander Shepard is appointed the first human Spectre, an elite agent operating outside conventional law on behalf of the Citadel Council. The appointment comes alongside an investigation into rogue Spectre Saren Arterius and his geth allies, which quickly reveals a threat far larger than anyone anticipated.
Open record →Sovereign, a Reaper using the geth as a proxy force, launches a direct assault on the Citadel. The battle is the conclusion of the events of Mass Effect 1 and results in Sovereign's destruction, though its implications for what is coming next are not fully understood by most of the galaxy.
Open record →Shortly after the Battle of the Citadel, Commander Shepard is killed during a Collector ambush in the Terminus Systems. The death sets up the events of Mass Effect 2 and the Cerberus Lazarus Project, which will take nearly two years to complete.
Open record →The Lazarus Project, a two-year effort by the human supremacist organisation Cerberus, successfully reconstructs and revives Commander Shepard. Shepard awakens to a galaxy that has changed and a new mission targeting the Collectors, who have been abducting human colonies across the Terminus Systems.
Open record →Shepard leads a handpicked team through the Omega-4 Relay into Collector space to destroy or capture the Collector base. No ship has previously returned from the relay. The mission's success depends entirely on the loyalty and capability of the team assembled beforehand.
Open record →The Reapers arrive in force at Earth and begin their harvest of the planet's population. The invasion triggers the galactic war that the first two games have been building toward, pulling every species into a conflict for survival that will determine the future of all organic life in the Milky Way.
Open record →The combined forces of the galaxy converge on Earth for a final push to reach the Citadel and activate the Crucible, a weapon designed to end the Reaper cycle. The Battle of London is the final military engagement of the Reaper War and the point from which Shepard makes their final choice.
Open record →In the Control ending, Shepard sacrifices themselves to become the guiding intelligence of the Reapers, redirecting the synthetic fleet away from destruction and toward a new purpose. The Reapers cease their harvest and depart, leaving a galaxy to rebuild without them.
Open record →In the Destroy ending, the Crucible releases an energy pulse that destroys all Reaper technology and synthetic life, including the geth and EDI. The mass relays are damaged and require extensive repair. Shepard may survive depending on the readiness of allied forces.
Open record →In the Synthesis ending, Shepard's body is converted into energy that spreads through the mass relay network, merging the DNA of all organic life with synthetic code. The distinction between organic and synthetic life is permanently dissolved across the galaxy.
Open record →The Andromeda Initiative launches its arks from the Milky Way, each carrying tens of thousands of colonists in cryogenic suspension for a 600-year journey to the Andromeda galaxy. The project was planned independently of the Reaper War and its arks are already in transit when the invasion begins.
Open record →The Ark Hyperion, carrying human colonists, arrives in the Heleus Cluster of the Andromeda galaxy after a 600-year journey. The conditions it finds there are significantly different from what the Initiative anticipated, and the Pathfinder must assess and respond to those conditions immediately.
Open record →Pathfinder Ryder leads the human colonisation effort in the Heleus Cluster of Andromeda in 2820, navigating conflict with the Kett, establishing relations with the native Angara, and working to make the cluster habitable for the Initiative's colonists. The events are entirely disconnected from the Milky Way's timeline.
Open record →Q: What year does Mass Effect take place?
Mass Effect 1 is set in 2183. Mass Effect 2 is set in 2185. Mass Effect 3 begins in 2186 and concludes later that year. Mass Effect: Andromeda is set in 2819 to 2820, after a 600-year journey to the Andromeda galaxy.
Q: What is the Mass Effect timeline in order?
Prothean ruins discovered on Mars (30 July 2148) → first relay activated (2149) → Systems Alliance founded (2151) → First Contact War with turians (April to June 2157) → Systems Alliance joins Citadel space (2165) → Shepard becomes first human Spectre, Mass Effect 1 begins (2183) → Battle of the Citadel, Sovereign destroyed (28 July 2183) → Shepard killed (2183) → Cerberus revives Shepard, Mass Effect 2 begins (August 2185) → Suicide Mission through Omega-4 Relay (24 December 2185) → Reaper invasion of Earth, Mass Effect 3 begins (6 March 2186) → Battle of London, Crucible activated (31 October 2186) → Andromeda Initiative arks arrive in Heleus Cluster (2819 to 2820).
Q: What are the three Mass Effect 3 endings?
The Destroy ending destroys all Reaper and synthetic life with the mass relays damaged. The Control ending has Shepard sacrifice themselves to become a guiding intelligence directing the Reapers. The Synthesis ending merges all organic and synthetic life into a new combined form of existence. All three occur on 31 October 2186.