The Northern line is one of two commuter rail routes operated by Merseyrail and centred on Merseyside, England, the other being the Wirral line. The cross-city route runs from Hunts Cross in south Liverpool then (by way of an underground section through Liverpool's city centre) branches in the north to terminate at Southport, Headbolt Lane (both Merseyside) and Ormskirk (Lancashire).

Passenger interchange to the Wirral line is available at Moorfields and Liverpool Central, and to the separately-owned City Line at Hunts Cross and Liverpool South Parkway. Liverpool South Parkway also allows interchange with regional and long-distance services, while connections to services operated by Northern Trains are possible at Headbolt Lane, Ormskirk and Southport.

This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Northern line" Merseyrail – news · newspapers · books · scholar · JSTOR (December 2022) (Learn how and when to remove this message)

The line runs from Hunts Cross in the south of Liverpool towards Liverpool Central. Brunswick station between St Michaels and Liverpool Central was added in 1998 to provide a connection to the Brunswick Business Park. In the tunnel just south of Liverpool Central, the line drops into a 1970s tunnel to a lower level into the underground Mersey Railway Liverpool Central (Low Level) station. North of Central the line uses the Mersey Railway tunnel for about half of the route to Moorfields, an underground station built in the 1970s to replace the surface-level Liverpool Exchange. North of Moorfields, the route emerges from the tunnel to join the Lancashire and Yorkshire Railway lines from the former Exchange station.

After Sandhills, the former Liverpool, Crosby and Southport Railway branches off towards Southport, while the other routes continue to Kirkdale on what was a joint section of track between Liverpool, Ormskirk and Preston Railway and the Liverpool and Bury Railway. After Kirkdale, the Ormskirk and Headbolt Lane lines diverge.

Generally, trains from Hunts Cross continue to Southport, while trains to Ormskirk and Headbolt Lane start at Liverpool Central. Daytime trains operate every 15 minutes on each of the three routes Monday to Saturday daytime and every 30 minutes evenings and Sundays. Until 2017, summer Sunday frequencies on the Southport route were increased to every 15 minutes. There are no peak hour frequency increases but trains on the Southport and Ormskirk routes are increased to six carriages, as are weekend services during the summer on the Southport route.

Special timetables are implemented for major events such as the Grand National meeting at Aintree and golf tournaments at Birkdale. These involve changing services on all branches and the closure of stations in anticipation of overcrowding risks.

Passengers from the year beginning April 2002 to the year beginning April 2022.

Station usage
Station name	2002–03	2004–05	2005–06	2006–07	2007–08	2008–09	2009–10	2010–11	2011–12	2012–13	2013–14	2014–15	2015–16	2016–17	2017–18	2018–19	2019–20	2020–21	2021–22	2022–23
Southport branch
Southport	1,080,767	1,549,576	1,582,115	1,669,056	1,681,444	3,094,576	2,949,656	2,886,448	2,675,304	2,496,384	3,980,176	4,129,340	4,147,064	4,240,372	4,140,152	4,271,792	4,710,560	1,266,712	3,094,396	3,339,582
Birkdale	164,753	251,641	256,424	270,277	289,106	820,240	783,066	770,104	734,950	702,168	915,232	954,774	999,758	1,035,000	1,051,252	1,257,834	1,361,614	337,370	851,710	974,514
Hillside	125,031	158,618	178,252	177,678	180,744	688,812	579,460	590,254	579,538	551,928	552,272	542,006	521,616	535,374	638,996	685,694	761,684	187,474	474,834	507,842
Ainsdale	210,317	289,260	322,911	328,423	345,791	998,438	955,328	972,616	960,772	899,420	956,960	983,858	1,004,554	1,023,510	928,028	1,016,242	1,127,850	321,382	768,028	920,626
Freshfield	169,370	249,567	266,415	277,933	283,772	827,718	798,444	795,312	760,336	715,288	740,700	771,648	777,812	773,750	721,168	712,078	773,250	205,926	484,074	498,888
Formby	279,822	424,875	482,312	525,841	553,546	1,668,128	1,576,974	1,595,890	1,513,544	1,401,584	1,282,716	1,311,918	1,385,228	1,492,202	1,476,462	1,516,340	1,547,950	418,070	995,964	1,062,658
Hightown	84,188	117,664	133,241	141,686	150,991	439,588	409,956	416,844	408,562	381,300	312,412	316,878	314,282	308,872	311,404	353,172	394,406	98,624	248,152	266,572
Hall Road	50,377	69,251	76,158	88,355	91,686	288,584	270,198	269,744	256,008	240,056	247,266	259,738	259,346	263,248	266,608	460,036	537,534	131,668	312,314	331,508
Blundellsands and Crosby	296,685	457,346	518,823	561,676	599,071	1,839,920	1,717,962	1,735,882	1,643,472	1,532,170	1,324,328	1,369,650	1,411,140	1,470,212	1,437,202	1,667,950	1,829,110	482,154	1,196,618	1,365,008
Waterloo	433,285	601,447	660,922	669,416	720,522	1,136,872	1,022,416	1,014,942	955,878	856,588	1,476,604	1,510,596	1,536,244	1,578,018	1,551,654	1,683,954	1,932,646	553,012	1,237,784	1,324,016
Seaforth and Litherland	176,145	300,292	335,884	337,209	362,341	832,894	766,468	789,156	761,342	684,324	731,628	750,192	759,314	764,674	790,704	871,670	1,019,398	351,030	715,640	880,034
Bootle New Strand	345,451	415,685	404,558	348,458	405,802	977,696	909,922	931,806	911,870	842,682	952,994	974,574	976,556	982,592	966,082	1,026,300	1,221,302	398,572	789,718	747,492
Bootle Oriel Road	57,791	155,295	203,956	249,030	209,041	523,944	511,614	521,576	511,164	475,814	598,050	617,332	642,868	637,608	649,772	787,114	842,670	224,108	503,766	584,074
Bank Hall	51,477	71,052	74,624	62,692	85,014	197,086	171,010	172,426	174,680	160,480	160,876	159,438	164,114	168,450	172,016	257,006	317,538	93,466	184,840	211,188
Ormskirk branch
Ormskirk	726,015	693,376	716,362	733,381	770,621	1,026,546	998,858	878,782	715,490	727,620	2,058,604	2,096,328	2,163,374	2,263,204	2,006,936	2,255,722	2,409,296	549,410	1,664,370	1,820,516
Aughton Park	95,060	86,413	83,012	89,200	85,699	124,736	109,592	96,224	78,530	78,136	179,740	183,340	187,670	200,604	180,544	204,282	218,496	37,232	112,192	139,550
Town Green	188,160	183,233	203,324	202,425	206,180	259,972	239,100	193,200	149,408	141,760	337,112	346,602	365,836	384,974	338,544	395,678	435,124	101,734	290,144	360,580
Maghull	394,191	431,945	502,020	610,318	696,791	2,144,046	1,999,436	1,956,936	1,863,098	1,745,454	1,765,756	1,821,492	1,812,534	1,865,348	1,870,086	1,639,668	1,789,936	463,100	1,106,204	1,164,994
Old Roan	177,332	260,871	284,901	305,589	337,166	918,262	861,176	863,568	815,704	748,070	864,554	896,562	903,968	921,306	930,812	1,006,706	1,185,406	320,184	787,518	847,726
Aintree	284,514	388,230	376,908	412,132	473,143	1,251,404	1,173,276	1,197,258	1,147,296	1,078,704	1,141,532	1,084,348	1,059,602	1,048,614	1,093,656	1,175,920	1,295,348	301,632	725,908	841,662
Orrell Park	369,037	452,889	473,979	469,256	491,948	1,257,746	1,170,676	1,192,140	1,186,210	1,088,622	1,031,132	1,040,358	1,032,522	1,057,416	1,035,218	1,124,446	1,313,788	355,900	813,262	1,052,986
Walton	65,155	93,261	110,471	113,214	113,131	179,148	162,612	164,478	159,384	141,182	269,260	272,784	271,828	261,742	248,896	450,148	571,226	151,334	334,012	418,168
Kirkdale	299,396	410,808	452,155	441,525	479,342	1,179,346	1,085,418	1,099,018	1,084,206	992,908	854,320	866,218	869,870	893,198	884,302	1,067,562	1,272,022	365,524	850,892	1,033,786
Kirkby branch
Kirkby	350,098	516,007	560,285	639,337	739,590	2,191,476	2,050,590	2,006,486	1,891,982	1,750,270	2,357,814	2,408,810	2,356,170	2,428,340	2,427,778	2,488,916	2,909,204	877,884	1,899,772	2,060,974
Fazakerley	215,019	300,552	329,306	318,664	330,843	889,816	832,474	864,108	861,054	789,698	1,061,930	1,088,202	1,088,808	1,108,962	1,135,988	1,250,320	1,465,622	413,542	920,166	899,436
Rice Lane	64,677	102,525	116,590	118,113	133,723	330,818	307,116	323,310	289,968	281,026	297,262	314,362	315,126	325,322	324,336	580,620	723,792	209,562	416,686	503,810
Kirkdale	See above	See above	See above	See above	See above	See above	See above	See above	See above	See above	See above	See above	See above	See above	See above	See above	See above	See above	See above	See above
Bank Hall\Kirkdale to Hunts Cross
Sandhills	178,991	272,009	314,309	306,134	207,944	390,346	446,210	495,458	501,448	471,804	1,250,086	1,324,068	1,321,020	1,323,174	1,325,892	1,088,132	1,298,784	341,714	815,288	778,764
Moorfields	339,533	309,014	383,815	1,577,540	2,141,398	5,141,655	4,445,984	4,637,356	6,363,434	6,049,491	6,541,235	6,832,585	6,996,347	7,173,567	7,365,918	6,534,016	7,361,420	1,613,112	4,807,882	5,100,886
Liverpool Central	1,086,536	982,498	1,293,790	7,169,618	8,856,570	19,635,814	18,413,982	17,958,028	14,224,147	13,522,391	14,621,585	15,272,837	15,638,894	16,035,031	16,464,993	14,605,446	16,454,940	3,605,780	10,747,030	11,401,980
Brunswick	224,476	352,854	407,134	410,813	442,711	1,061,698	979,312	963,252	1,007,874	908,670	829,356	871,856	929,958	1,037,186	1,032,192	1,128,162	1,273,262	311,496	696,788	782,698
St Michaels	195,408	289,183	365,547	360,976	378,944	562,860	506,288	469,570	466,728	387,532	873,112	936,740	977,510	1,006,394	1,010,820	1,128,708	1,308,664	349,670	785,816	950,870
Aigburth	146,283	179,458	241,063	246,583	265,442	761,362	696,992	681,774	702,378	614,374	686,496	746,784	833,452	812,582	743,410	864,238	974,200	203,034	483,488	567,018
Cressington	74,789	120,034	152,383	164,734	170,409	456,042	424,174	421,076	427,480	386,376	463,148	477,112	476,636	490,986	517,108	636,070	750,210	181,814	432,612	484,174
Garston	141,022	190,778	222,247	42,886	Closed	Closed	Closed	Closed	Closed	Closed	Closed	Closed	Closed	Closed	Closed	Closed	Closed	Closed	Closed	Closed
Liverpool South Parkway	—	—	—	288,845	419,681	568,822	581,898	641,662	733,698	740,414	1,785,444	1,803,308	1,893,958	1,983,726	2,247,290	2,745,588	2,663,414	573,572	1,460,056	1,812,630
Hunts Cross	277,961	326,258	443,837	464,367	503,426	1,269,710	1,190,934	1,172,150	1,160,738	1,062,798	1,289,590	1,364,502	1,410,366	1,450,268	1,446,138	1,452,752	1,827,454	530,966	1,155,580	1,307,550
The annual passenger usage is based on sales of tickets in stated financial years from Office of Rail and Road estimates of station usage. The statistics are for passengers arriving and departing from each station and cover twelve-month periods that start in April. Methodology may vary year on year. Usage from the periods 2019-20 and especially 2020-21 onwards have been affected by the Covid-19 pandemic

There are a total of 11 trains per hour (tph) running on the central section between Sandhills and Liverpool Central. The service pattern is: (Not all stops listed; trains call at every station on their route.)

Northern Line
Route	tph
	Mon.–Sat.	Sun.
Southport–Formby–Sandhills–Liverpool Central–Liverpool South Parkway–Hunts Cross	4	2
Ormskirk–Sandhills–Liverpool Central	4	2
Headbolt Lane–Sandhills–Liverpool Central	3	2

The Northern Line was introduced in 1977.

In 2006, Garston station was replaced by Liverpool South Parkway station.

The line is electrified using 750 V DC third rail, identical to the third rail system present in southern England.

• Liverpool Exchange to Southport, Crossens and Meols Cop was the first section to be electrified, in 1904.
• The branch to Aintree, on the Ormskirk branch, followed in 1906, extended to Ormskirk in 1913.
• The Headbolt Lane branch and the line south to Garston were electrified to create a north–south line through the Link Tunnel in 1978.
• Electrification was cut back to Southport in the north in 1964 as part of the Southport-Preston line closure, stations closing which previously had had electric services were St Lukes, Hesketh Park, Churchtown, and Crossens, electric services also ceased to Meols Cop station although the conductor rail remained until 1970 to serve the large depot at Meols Cop, and this station continues to serve trains on the Southport to Wigan/Manchester line.
• Garston to Hunts Cross was electrified in 1983.

Interchange with the Wirral line is available at Liverpool Central and Moorfields. As the Northern line does not pass through Liverpool Lime Street, passengers from other rail networks must use the Wirral line as a connection. As there is only a direct escalator down to the Wirral line towards Birkenhead at Liverpool Central and given the short distance between Central and Lime Street most passengers prefer to walk rather than use the several escalators necessary to travel between the two stations.

Liverpool city centre stations have lifts for wheelchairs buggies and heavy luggage but they are small.

Interchange with other National Rail services can be made at Southport, Ormskirk, Headbolt Lane, Liverpool South Parkway and Hunts Cross.

Liverpool South Parkway opened on 11 June 2006, replacing Garston and providing connections to the City Line formerly available at Allerton.

Plans to re-open St James station have been proposed. Merseytravel agreed to work with Liverpool Vision in March 2014 to investigate the cost of re-opening the station and its projected usage. Merseytravel listed the re-opening of St James station as a 'top rail project' on a Rail Development and Delivery Committee report in 2016.

As part of Lancashire County Council's plans to build a new railway station in Skelmersdale, they proposed an extension to the Northern Line that would change the terminus of the Kirkby branch of the line from Kirkby (now Headbolt Lane) to Skelmersdale. The proposals could see Merseyrail services also passing through Rainford railway station. By September 2017, Merseytravel and Lancashire County Council had committed £5 million of funding to the scheme. Merseytravel believe the scheme could cost around £300 million to develop and could be ready in a decade.

Liverpool City Region Combined Authority, Long Term Rail Strategy document of October 2017, page 37, states a review in 2020 to introduce new Merseyrail battery trains will be undertaken, in view to put Preston onto the Merseyrail network by extending the Merseyrail Northern Line from Ormskirk to Preston. The aim is to have Preston one of the terminals of the Northern Line. The document states, "The potential use of battery powered Merseyrail units may improve the business case".

• LYR electric units
• A59 road, which follows the same route.

• Media related to Northern Line (Merseyrail) at Wikimedia Commons

53°24′16″N 2°58′47″W / 53.4045°N 2.9798°W / 53.4045; -2.9798