The M4 is a long motorway in the United Kingdom. It goes from London to South Wales. It also passes Bristol. It was first called the London–South Wales Motorway.

Junctions
{| style="margin-left:1em; margin-bottom:1em; color:black; font-size:90%;" class="wikitable"
|-  style="background:#0080d0; text-align:center; color:white; font-size:120%;"
| colspan="5" | M4 motorway
|-
!scope=col|mile
!scope=col|km
!scope=col abbr="Eastbound"|Eastbound exits (B carriageway)
!scope=col|Junction
!scope=col abbr="Westbound"|Westbound exits (A carriageway)
|- style="text-align:center;"
|7.3
|11.8
|Road continues as A4 to Central London
|J1
| Start of motorway
|- style="text-align:center;"
|8.38.5
|13.4  13.7
| North Circular A406South Circular A205Chiswick A315
|J2
| Staines, Hounslow, Brentford A4
|- style="text-align:center;"
|12.512.8
|20.120.6
|Heston services
|Services
|Heston services
|- style="text-align:center;"
|13.413.7
|21.5  22.1
| Heathrow  (Terminals 4, 5 & Cargo), Hayes, Harrow, Hounslow A312
|J3
| Heathrow  (Terminals 4, 5 & Cargo), Hayes, Harrow, Hounslow A312
|- style="text-align:center;"
|15.215.7
|24.5  25.2
| Heathrow  (Terminals 2 & 3) (A4) Uxbridge A408
|J4a
| Heathrow  (Terminals 2 & 3) (A4) Uxbridge A408
|- style="text-align:center;"
|16.817.7
|27.0  28.5
| Heathrow (Terminals 4, 5 & Cargo) , Gatwick Airport , Watford (M3), (M23), (M40), (M1) M25
|J4b
| Heathrow (Terminals 4, 5&Cargo), Gatwick, Watford (M3), (M23), (M40), (M1), M25
|- style="text-align:center;"
|19.119.5
| 30.7 31.4
| Colnbrook, Langley, Slough (East) A4Eton, Datchet B470
| J5
| Colnbrook, Langley, Slough (East)  A4, Datchet B470
|- style="text-align:center;"
|22.923.2
| 36.8  37.4
| Slough (Central) A355Windsor A322
|J6
| Slough (Central) A355Windsor A322
|- style="text-align:center;"
|24.725.0
| 39.8  40.3
| Slough (West) A4
|J7
| Slough (West) A4
|- style="text-align:center;"
|27.828.2
| 44.7  45.4
| High Wycombe, Henley A404(M)Maidenhead A308(M)
|J8/9
| High Wycombe, Henley A404(M)Maidenhead A308(M)
|- style="text-align:center;"
|35.035.8
| 56.4  57.6
| Reading (East), Wokingham, Bracknell A329(M)
|J10
| Reading (East), Wokingham, Bracknell A329(M)
|- style="text-align:center;"
|40.641.2
|65.4 66.3
| Basingstoke, Reading (Central & South) A33
|J11
| Basingstoke, Reading (Central & South) A33
|- style="text-align:center;"
|43.543.8
|70.0 70.5
|Reading services
|Services
|Reading services
|- style="text-align:center;"
|45.345.7
| 72.9 73.5
| Reading (West), Theale A4
|J12
| Reading (West), Theale A4
|- style="text-align:center;"
|56.957.2
|91.5  92.1
| Newbury, Oxford A34Chieveley services (Moto)
|J13Services
| Newbury, Oxford A34Chieveley services (Moto) 
|- style="text-align:center;"
|64.464.8
|103.7  104.3
| Hungerford, Wantage A338
|J14
| Hungerford, Wantage A338
|- style="text-align:center;"
|68.7
|110.5
|Membury services
|Services
|Membury services
|- style="text-align:center;"
|76.477.1
|122.9  124.0
| Swindon (East) A419Marlborough A346Oxford (A420)
|J15
| Swindon A419, Marlborough A346
|- style="text-align:center;"
|82.482.8
|132.6  133.2
| Swindon (West), Royal Wootton Bassett, Wroughton, MoD Lyneham, Calne A3102
|J16
| Swindon (West), Royal Wootton Bassett, Wroughton, MoD Lyneham, Calne A3102
|- style="text-align:center;"
|94.895.3
|152.5  153.4
| Chippenham A350Cirencester A429
|J17
| Chippenham A350Cirencester A429
|- style="text-align:center;"
|96.7
|155.7
|Leigh Delamere services
|Services
|Leigh Delamere services
|- style="text-align:center;"
|104.9105.6
|168.8  170.0
| Bath, Stroud A46
|J18
| Bath, Stroud A46
|- style="text-align:center;"
|112.8113.2
|181.5  182.1
| Bristol M32
|J19
| Bristol M32
|- style="text-align:center;"
|115.8116.3
|186.3  187.2
| The SOUTH WEST, Bristol (West), The MIDLANDS, Gloucester, Bristol Airport , M5    
|J20Almondsbury Interchange
| The SOUTH WEST, Bristol (West) M5(S) The MIDLANDS, Gloucester M5(N)
|- style="text-align:center;"
|117.7189.5
|189.5  190.0
|No access
|J21
| Chepstow M48
|- style="text-align:center;"
|121.3121.6
|195.2  195.7
| Avonmouth M49
|J22
| Avonmouth M49
|- style="text-align:center;"
|121.7124.1
|195.9199.8
|Entry into England
| Second Severn Crossing
|Entry into Wales
|- style="text-align:center;"
|127.0
|204.4
| No toll plaza
| Bridge Toll
| style="background:#dcdcfe;"| Former Toll plaza (closed Dec 2018)
|- style="text-align:center;"
|129.2
|208.0
| Chepstow M48
|J23
|No access
|- style="text-align:center;"
|131.4132.2
|211.4212.8
| Magor, Caldicot A4810Magor services
|J23A  Services
| Magor, Caldicot A4810 Magor services
|- style="text-align:center;"
|134.8135.6
|217.0218.3
| City centre A48Newport (East) B4237Monmouth A449The MIDLANDS (M50)
|J24
| City centre A48Newport (East) B4237Monmouth A449
|- style="text-align:center;"
|137.9
|222.0
|No access
|J25
| Caerleon B4596
|- style="text-align:center;"
|138.3
|222.6
|No access
|J25A
| Newport, Cwmbran A4042
|- style="text-align:center;"
|138.8139.1
|223.4223.8
|Brynglas Tunnels
|Tunnel
|Brynglas Tunnels
|- style="text-align:center;"
|139.1139.5
|223.8224.5
| Newport, Cwmbran, Caerleon A4051
|J26
| Newport A4051
|- style="text-align:center;"
|140.8141,4
|226.6227.6
| High Cross B4591
|J27
| High Cross B4591
|- style="text-align:center;"
|142.0142.9
|228.5230.0
| Newport A48Risca, Brynmawr A467
|J28
| Newport A48Risca, Brynmawr A467
|- style="text-align:center;"
|143.6
|231.1
|No access
|J29
| Cardiff (East and South) A48(M)
|- style="text-align:center;"
|146.6147.3
|236.0237.0
| Cardiff (East) A4232Cardiff Gate services
|J30  Services
| Cardiff (East) A4232Cardiff Gate services
|- style="text-align:center;"
|151.9244.5
|244.5246.1
| Merthyr Tydfil, Cardiff A470
|J32
| Cardiff (North), Merthyr Tydfil A470
|- style="text-align:center;"
|155.4156.0
|250.1251.1
| Cardiff (West), Barry, Penarth A4232Cardiff Airport Cardiff West services
|J33Services
| Cardiff (West), Barry, Penarth A4232Cardiff Airport Cardiff West services
|- style="text-align:center;"
|157.5158.1
|253.5254.4
| Llantrisant, Rhondda A4119Royal Glamorgan Hospital
|J34
| Llantrisant, Rhondda A4119Royal Glamorgan Hospital
|- style="text-align:center;"
|163.9164.4
|263.7264.5
| Pen-coed A473
|J35
| Bridgend, Pen-coed A473
|- style="text-align:center;"
|167.5168.3
|269.6270.8
| Bridgend A4061Maesteg A4063Princess of Wales HospitalSarn Park services
|J36Services
| Bridgend A4061Maesteg A4063Princess of Wales HospitalSarn Park services
|- style="text-align:center;"
|172.8173.5
|278.1279.3
| Pyle, Porthcawl A4229
|J37
| Porthcawl, Pyle A4229
|- style="text-align:center;"
|177.0177.3
|284.9285.3
| Port Talbot A48
|J38
| Port Talbot A48
|- style="text-align:center;"
|178.3
|286.9
|No access (on-ramp only)
|J39
|No access
|- style="text-align:center;"
|179.7179.9
|289.2289.6
| Port Talbot A4107
|J40
| Port Talbot A4107
|- style="text-align:center;"
|180.9181.3
|291.1291.8
| Port Talbot A48
|J41
| Briton Ferry A48
|- style="text-align:center;"
|183.9184.9
|295.9297.3
| Briton Ferry A48Swansea (South) A483
|J42
| Swansea (South) A483
|- style="text-align:center;"
|184.9185.7
|297.5298.8
| Neath, Merthyr Tydfil A465
|J43
| Neath, Merthyr Tydfil A465
|- style="text-align:center;"
|187.0187.4
|300.9301.6
| Swansea (East) A48
|J44
| Swansea (East) A48
|- style="text-align:center;"
|188.8189.3
| 303.9304.7
| Pontardawe, Swansea (North) A4067
|J45
| Pontardawe, Swansea (North) A4067
|- style="text-align:center;"
|190.8191.4
| 307.0308.0
| Llangyfelach B4489FelindreMorriston Hospital
|J46
| Llangyfelach B4489FelindreMorriston Hospital
|- style="text-align:center;"
|192.4193.1
|309.6310.7
| Swansea (West) A483Gorseinon A48Swansea services
|J47Services
| Swansea (West) A483Gorseinon A48Swansea services
|- style="text-align:center;"
|196.4197.1
|316.0317.2
| Pontarddulais, Llanelli A4138
|J48
| Pontarddulais, Llanelli A4138
|- style="text-align:center;"
|199.2
| 320.6
| Start of motorway
|J49TerminusServices
| Motorway terminates at a roundabout:Carmarthen A48Ammanford, Llandeilo A483Pontarddulais A48Pont Abraham services
|-

References

Coordinates

Motorways in England
Motorways in Wales