Never forget.

Dozens of events this week will honor the memories of those killed during the Sept. 11, 2001 terror attacks — and the first responders who survived the harrowing ordeal — as well as to celebrate the unity in the aftermath that rebuilt the Big Apple.

The 25th anniversary of the horrifying attacks that claimed the lives of 2,977 civilians and heroes — almost all of whom were killed at Ground Zero — will take place on Friday.

Hundreds more have since died from illnesses and injuries tied to 9/11.

Here are just some of the major events happening in New York City this week:

Wreath-laying ceremony

The NYPD Detectives’ Endowment Association will host a wreath-laying ceremony with Gov. Kathy Hochul, Police Commissioner Jessica Tisch and the family of two brothers who were killed trying to save lives on 9/11, at Ground Zero on Tuesday.

The 11:45 a.m. ceremony is dedicated to NYPD Detective Joseph V. Vigiano and his brother, FDNY Firefighter John Vigiano, as well as NYPD Detective Claude “Dan” Richards, all of whom rushed into the burning World Trade Center but never came home.

The service will also honor the 79 NYPD detectives who later died from illnesses connected to their rescue, recovery and investigative work on September 11.

NYPD remembrance wall dedication

The NYPD will dedicate a new remembrance wall on Wednesday in honor of the first responders who were slain in the attacks, and the hundreds who have since succumbed to illness and injuries tied to the tragedy.

The new wall at One Police Plaza will recognize close to 500 heroes.

Engineering Resilience

The American Council of Engineering Companies of New York is hosting a special event Thursday to honor the largely unsung heroes who aided the response and recovery of the September 11 attacks.

The “Engineering Resilience: 25 Years of Rebuilding, Remembrance and Renewal” will include discussions and keynote addresses on the response to structural conditions in the aftermath of the attacks, the ensuing investigation and the evolution of building code regulations, as well as the redevelopment of the downtown community.

The event at The Union League Club will kick off at 8 a.m.

Ride for Resilience

More than 200 firefighters, including dozens who responded to the terrorist attack, their loved ones and supporters will conclude their 343-mile cycling journey at the World Trade Center on Thursday.

The group covered the incredible route from Boston over five days in honor of those who were lost in the tragedy — and those who continue to live today with the 9/11-related illnesses and the mental weight of their duties.

The emotional arrival at Ground Zero will conclude with a moment of silence at the 9/11 Memorial and a 2 p.m. ceremony at Battery Park — which includes a performance by singer Carolina Rial, whose father died from a cancer tied to his days working in Manhattan during the attacks.

St. Patrick’s Mass

St. Patrick’s Cathedral is hosting a special Mass in honor of the 25th anniversary at 5 p.m. on Thursday.

Archbishop Ronald Hicks has invited all bishops throughout the Empire State to attend the event, which is invitation- and ticket-only, but will be livestreamed on the church’s website and YouTube.

A second ceremony is scheduled for the following day at 2 p.m., shortly after the annual 9/11 Memorial & Museum ceremony concludes.

The NYPD pipe and drum band, as well as 12 other bands from around North America, will attend.

Steel Across America Tour conclusion

After traveling more than 10,500 miles across the country as part of a moving memorial, a massive piece of steel recovered from Ground Zero will return to the World Trade Center on Friday.

The family of fallen FDNY hero Stephen Siller at 5 a.m. will retrace his final journey through the Brooklyn-Battery Tunnel, which he famously ran through in his gear to respond to the terror attacks.

The solemn ceremony will serve as the conclusion of the Steel Across America Tour, a nearly five-month-long tour that was launched in part to help enlighten kids who weren’t alive at the time.

9/11 Memorial Ceremony

The annual remembrance ceremony at Ground Zero will begin at 8:40 a.m. and will be livestreamed.

The first of seven moments of silence will come at 8:46 a.m. in observance of when hijacked Flight 11 struck the North Tower, followed by the reading of names of the 2001 and 1993 WTC bombing victims by the loved ones they left behind.

For the first time, there will be a seventh moment of silence to honor those who have since died from 9/11-related illnesses and injuries.

Tribute in Light

The annual 9/11 Memorial & Museum Tribute in Light will illuminate the Big Apple’s skies as the sun sets on Friday and will last until dawn on Saturday morning.

The lights will shine from where the Twin Towers once stood at Ground Zero.

Dozens of other iconic buildings throughout the five boroughs — and across the US — will also illuminate their facades and rooftops in blue to coincide with the art installation.

The Memorial Plaza will be open to the public starting at 3 p.m. to allow the public to view the installation, and the annual Tribute in Light for the first time will be aired in a live national broadcast on Disney-affiliated channels and streamers.

Subway Series

The Mets and Yankees will face off in the Bronx for the first of their three-game series Friday.

The 6:30 p.m. game will kick off with a ceremony to honor the 25th anniversary and will include special tributes honoring first responders and those lost in the attacks.

Madison Square Garden Theater Concert

The NYPD Pipes and Drums will perform “A Night of Remembrance – 25th Anniversary 9/11 Memorial Concert” at the Infosys Theater at MSG on Saturday.

Radio personality Sid Rosenberg will serve as the Master of Ceremonies, and the concert will also include other guest pipe bands as well as a special performance by Irish tenor Dr. Ronan Tynan.

A post-concert party will be held at the Manhattan Center Grand Ballroom with music by Shilelagh Law.

Doors open at 6 p.m. and tickets are available for $150.

Museum exhibit opening

The 9/11 Memorial & Museum will open Saturday with a landmark special exhibition: “In Their Honor: 25 Years of 9/11-Inspired Service.”

The new exhibit examines how individuals and communities transformed their grief into action in the wake of the tragedy — and how their service continues to impact the Big Apple 25 years later.

The new exhibition includes a helmet of an FDNY firefighter inspired to follow in his father’s footsteps after the hero died on 9/11, a massive papier-mâché phoenix sculpture made by children who lost loved ones in the attack, and much more.