The Prophet says:"Twelve imams will come after me." Bukhari, Muslim,etc.
Twelve Imams are:
1-Imam Ali ibn-i Ebu Talib.
2- Imam Hasan Müçteba.
3-Imam Hüseyin Seyyid-us Süheda.
4- Imam Ali Zeynülabidin.
5- Imam Muhammed Bâkir.
6- Imam Cafer Sadik.
7- Imam Musa Kazim.
8- Imam Ali Riza.
9- Imam Muhammed Taki.
10- Imam Ali Naki.
11- Imam Hasan Askeri.
12- Imam Mehdi Kâim.
Useful information: There is a large body of ahadeeth in the Sunni books of reference on the number of the Imaams after the Holy Prophet. Naturally there are not as many ahadeeth in such books on the names of the twelve Imaams. Two important authors from the Sunni school of thought who come to mind immediately are: (1) Shaikh Sulayman Balkhi (died 1294 AH). In his Yanabi-ul-Mawadda, Ch.76, reports the following hadith- A jew name Na'thal came to the Holy Prophet (SAWA) and questioned him about Tawheed and was so impressed with the answers given that he embraced Islam. Then Na'thal asked about his (the Prophet's) vicegerents. The Prophet answered, "My vice-gerent is Ali bin Abi Taalib, after him his son Hassan, then Hassan's brother Hussain who will be followed by his nine successive descendants." The Holy Prophet named all the Imaams. The author also reports from the Manaqib of Khawarizmi another hadith on the same lines originating from Jabir bin Abdullah (Ansari). (2) In Kifayatul Athar there is a tradition from Jabir bin Abdullah Ansari who reports that when Ayah 62 Surah 4, "O you who believe, obey Allah, and obey the Apostle and those among you who are invested with authority" was revealed, Jabir asked who the persons invested with authority were. The Holy Prophet said, "They are my khulafah as well as the Imaams of the Muslims." He went on to name the Imaams. When he got to Imaam Muhammad al-Baqir, he paused and told Jabir, "O Jabir, you will meet him and when you do so, convey my salaams to him". The Prophet then went on to name the remaining Imaams and describe the minor and the major occultations of the twelfth Imaam. There are many ahadeeth from the Shiah sources. Ayatullah Ibrahim Amini in his al-Imaam al-Mahdi reports the following hadith from Jami' ahadeeth al-Shiah, Vol. 1, Introduction: Hazrat Ali (AS) in one of his khutbas mentioned the hadith from the Holy Prophet giving the details of the twelve Imaams and asked the congregation to confirm the hadith which they unanimously did.