Yes. With the Messages resource URI, you can send and receive messages containing up to 1,600 characters in standard GSM encoding, or up to 670 if Unicode characters are used. These long SMS are called concatenated messages.
For extensive details on how GSM vs. Unicode encoding works, and how this relates to concatenated messages, see: What the Heck is a Segment?
Sending outbound concatenated SMS
Concatenated messages are supported when sending to all major US/Canada carriers except for Sprint. Sprint does not support concatenated SMS. Many carriers worldwide as well as many smaller US/Canada carriers also support concatenated messages.
When sending concatenated SMS, Twilio will auto-segment long messages with a special header, which mobile carriers can use to reassemble the segments on the destination handset. Thus, concatenated SMS can appear as one single message on the receiving device.
Refer to our FAQ for how pricing works for outbound concatenated messages.
See also: What the Heck is a Segment? for extensive detail on SMS segmentation.
What happens when sending to a carrier that does not support concatenated messages?
Even if a mobile carrier does not support concatenated messages, you can still send long SMS to recipients on that carrier. Twilio will divide your long message into individual SMS to meet the character limit, and automatically add page information to the beginning of each one, for example (1/2), (2/2). On Twilio, your message will still appear under a single Message SID.
A note about US Cellular: 150-character limit
In addition to not supporting concatenated messages, US Cellular also limits the length of a single message to 150 characters, instead of 160. This means that long messages to US Cellular may segment slightly differently than those to other networks.
Receiving inbound concatenated SMS
Similarly, Twilio supports inbound concatenated messages up to 1,600 characters. Inbound messages over 160 characters long will be received on your Twilio phone number as one single message, as long as the sending carrier supports concatenation. The price of the inbound message will be the sum of the total number of segments.