The Orange Order says flagship parades in Portadown and Kilkeel will provide "an enhanced cultural experience" for spectators.
The parades mark the 326th anniversary of King William III's victory at the Battle of the Boyne in 1690.
Here are all the details of the 12 July celebrations, including parade locations and routes.
Portadown - Flagship Twelfth
The Orange Order expects 5,000 members to take part in the parade, along with 80 bands.
The main parade will commence at 10:15 BST, and proceed through the town centre via Bridge Street, High Street, Market Street and Church Street to the demonstration field on the Armagh Road.
Kilkeel - Flagship Twelfth
One thousand Orangemen are expected to take part, with 14 of the 15 lodges  accompanied by their own band.
Kilkeel lodges will leave Kilkeel Orange hall at 09:30 BST and walk several miles to the Council Road on the outskirts of the town. Here they will be joined by other district lodges.
The parade will then proceed via Newcastle Road, Newcastle Street and Greencastle Road, to the demonstration field at Manse Road.
Belfast
This year's Belfast parade will leave Belfast Orange Hall, at Carlisle Circus, at 10:00 BST, making its way along Clifton Street, Donegall Street, Royal Avenue, Castle Junction, and Donegall Place to Belfast City Hall.
A wreath-laying ceremony will take place at the Cenotaph in the grounds of the City Hall. This year the service marks the 100th anniversary of the Battle of the Somme and those who served with the 36th Ulster Division.
At 10:40 BST, the parade will then proceed via Donegall Square West, Bedford Street, Dublin Road, Shaftesbury Square, Bradbury Place, Lisburn Road, Balmoral Avenue and Malone Road to the demonstration field at Barnett Demesne.
Around 60 bands will walk the six-mile route, traditionally the longest of all the Twelfth demonstrations.
The parade is due to leave the field for the return leg at 16:15 BST.
Maguiresbridge
Orangemen from Donegal, Leitrim, Cavan and Monaghan will join 90 lodges and 70 bands from Northern Ireland.
This year, to commemorate the centenary of the Battle of the Somme the parade will be headed by soldiers dressed in First World War period costume.
Lodges and bands will move off at 12.30 BST from the assembly point at Killyshambley on the Tempo Road before proceeding through the village to the demonstration field on the Lisnaskea Road.
Limavady
The Limavady demonstration will be the largest Orange parade in County Londonderry.
Approximately 3,000 Orangemen, representing 60 lodges, will be accompanied by over 50 bands.
The main procession will commence at 12:00 BST from Church Street.
It will move through the town centre via Ballyclose Street, Main Street, Linenhall Street, Catherine Street, Roemill Road, William Street, Protestant Street, Catherine Street, Irish Green Street and Roemill Gardens to the Limavady Orange field.
Castledawson
Up to 50 bands will accompany around 60 Orange lodges as the village hosts the Twelfth for the first time since 2001.
The main parade will set off at 12:00 BST from the Hill Road. It will then proceed across the River Moyola and through the village to the demonstration field on the Magherafelt Road.
Coagh
One of Tyrone's smallest villages will play host to the county's largest Twelfth parade.
Upwards of 70 lodges will be accompanied by over 50 bands.
The main procession will set off at 12:30 BST from the assembly field on the Ruskey Road, before proceeding down Tamlaght Hill, Coagh Bridge and through the village to the demonstration field on the Drumconvis Road.
Newtownstewart
Over 5,000 people are expected to take part in the Twelfth demonstration in Newtownstewart, which is hosting the annual parade for the first time since 2010.
The main parade will move off at 12:30 BST from the assembly field on the Strabane Road and proceed along Millbrook Lane, Mourne Park, Oldcastle Road, Dublin Street, Main Street, Castle Brae, Douglas Road via The Old Bridge, Castle Brae via Abercorn Bridge to the demonstration field at Miller's Holm.
Aughnacloy
Twenty five lodges from two districts, Annahoe and Fivemiletown, will be on parade.
They will be accompanied by a number of lodges from County Monaghan.
The parade will assemble on the Caledon Road, moving off at 12:30 BST.
It will proceed along Moore Street to the fingerpost at Augher Road, before returning via Moore Street to the demonstration field at Aughnacloy College.
Donaghadee
More than 50 lodges will be on parade and a large number of Orangemen from England and Scotland are also expected.
The main parade will move off at 12:00 BST and proceed via Warren Road, Shore Street, the Parade, Manor Street and Millisle Road, to the demonstration field at the Commons.
To mark the centenary of the Battle of the Somme, the parade will be led by re-enactors dressed in period World War One uniforms.
Comber
Almost 70 lodges and 40 bands will take part in the Twelfth in Comber.
The main parade will commence at 12:30 BST from Park Way playing fields and will proceed through the town via Park Way, Killinchy Street, the Square, High Street, Braeside, Ballygowan Road, Railway Street, Orange Hall Lane, Brownlow Street, Glen Road, Mill Street, Castle Street, Bridge Street Link, Bridge Street, the Square, Killinchy Street and Park Way.
The parade will then return to the playing fields for a religious service.
Dromore
The Orange Order expects as many as 20,000 spectators at the biggest demonstration County Down.
The main parade will leave Ballymacormick Road at 12:00 BST and parade through the town centre to the demonstration field, located on the Lurgan Road.
Randalstown
On the centenary of the Battle of the Somme, participants in the Randalstown parade will symbolically proceed to the town's Dunmore Park, which was used as a military training camp during the First World War.
The main parade will leave Shane Street at 11:00 BST and proceed through the town on its way to Dunmore Park.
The return parade is due to commence at 16:00 BST.
Lisburn
More than 70 Orange lodges will take part in the Lisburn parade, accompanied by approximately 50 bands.
The parade is scheduled to get underway at 11:30 BST, commencing from the assembly point at Wallace Park.
It will then proceed through the city via Magheralave Road, Railway Street, Market Square, Market Street, Smithfield Street, Market Place, Governors Road, Thiepval Road, Prince William Road and Knockmore Road to the demonstration field at Ballymacross playing fields.
Ballymena
Upwards of 30 lodges and accompanying bands will take part in the annual Twelfth in Ballymena.
The town is the only one in Northern Ireland which has a Twelfth parade every year.
Orangemen and 15 bands will assemble at Wakehurst Road at 12:30 BST and proceed through the town via Queen Street, Harryville Bridge, Waveney Road, Galgorm Road, Pentagon, Lower Mill Street, Ballymoney Street and Thomas Street to the People's Park on the Doury Road.
Glenarm
Eleven lodges, comprising over 400 Orangemen, will be accompanied by eight bands and a number of Lambeg drums.
The main parade, commencing at 12:00 BST, will proceed through the village from the assembly point on the Coast Road via Mark Street, the Vennel, Coast Road and Ballymena Road to the field at Straitkeilly Road.
Ahoghill
A total of 16 lodges accompanied by nine bands will take part in this parade, along with numerous Lambeg drummers.
The main parade will commence from the Galgorm Road/Killane Road junction at 12:30 BST, and then proceed towards the village centre via the Portglenone line, Glebe Road, Church Street, through the Diamond area to the village playing fields on the Cullybackey Road.
Ballycastle
Over 40 lodges from five districts will take part in the Ballycastle parade, accompanied by around 30 bands and a number of Lambeg drums.
The outward route will proceed via Ramoan Road, Church Road, Coleraine Road, Castle Street, the Diamond, Ann Street, Rathlin Road, Strandview Road, North Street, Quay Road to Quay Road playing fields for the religious service.
A total of 18 demonstrations are being held as part of the Twelfth of July commemorations on Tuesday.